目錄
Japanese “らしい” does not simply mean “I heard that.” It has two main directions of meaning. When attached to a clause, it often expresses hearsay or inference based on indirect information. When attached to a noun, it can describe someone, a season, or a thing as having the typical characteristics associated with that noun. For example, “雨が降るらしい” means that apparently it is going to rain, while “春らしい天気” describes weather that feels characteristically spring-like. The function of “らしい” is completely different in these two sentences.
Expressions such as “彼らしい答え” and “京都らしい町並み” are not separate grammar patterns. They are extensions of the typicality use of “noun＋らしい.” The noun becomes the standard against which something is judged, describing a choice, way of speaking, or scenery as fitting the established impression of that person or place. When you see “らしい,” first check whether what comes before it is a complete proposition or a noun being used as a standard. That usually makes the intended meaning much easier to identify.
What Does “らしい” Mean? Hearsay and Inference vs. “Typical of…”
The first important use of “らしい” is to indicate that, based on something heard, a news report, a rumor, or other indirect information, the speaker believes something is probably true. Depending on the context, it can be translated as “apparently,” “I heard that,” “it seems,” or “reportedly.”
For example, “田中さんは来月転勤するらしい” means that the speaker has some relevant information suggesting Tanaka will be transferred next month, but is not presenting it as a fact personally confirmed. Compared with the hearsay “〜そうだ,” which is more directly used to relay information obtained from another source, “らしい” more easily retains the nuance that the speaker has formed a judgment based on indirect information.
The other major use is “noun＋らしい.” Here, “らしい” means that a person or thing has characteristics typically associated with that noun, as in “春らしい天気,” “子どもらしい笑顔,” and “彼らしい考え方.” In this use, there is no meaning of “I heard that” at all.
- Example: 田中さんは来月、転勤するらしいです。
Kana: たなかさんはらいげつ、てんきんするらしいです。
Translation: Apparently, Mr. Tanaka is being transferred next month.
The speaker judges from indirectly obtained information that the transfer is probably true, without implying personal confirmation. - Example: 今日は春らしい暖かい一日でした。
Kana: きょうははるらしいあたたかいいちにちでした。
Translation: Today was a warm day that really felt like spring.
“春らしい” means that the temperature and overall atmosphere match the typical image of spring. It has nothing to do with hearsay. - Example: それは彼らしい答えですね。
Kana: それはかれらしいこたえですね。
Translation: That really is an answer typical of him.
“彼” becomes the standard of comparison, and the answer matches what the speaker already knows about that person.
Japanese “らしい” Conjugation Rules: How Do Verbs, Adjectives, and Nouns Connect?
The hearsay and inference use of “らしい” can follow verbs, い-adjectives, な-adjectives, and nouns. Verbs and い-adjectives generally use their plain forms. With な-adjectives and nouns in the affirmative present form, “だ” is omitted and “らしい” attaches directly.
The typicality use of “らしい” mainly follows nouns. The entire expression then behaves like an い-adjective, allowing forms such as “らしく,” “らしくない,” and “らしかった.”
| Use | Structure | Example | Meaning |
|---|---|---|---|
| Hearsay／Inference | Plain-form verb＋らしい | 雨が降るらしい | Apparently／it seems it will rain |
| Hearsay／Inference | Plain-form い-adjective＋らしい | 忙しいらしい | Apparently busy |
| Hearsay／Inference | な-adjective stem＋らしい | 元気らしい | Apparently doing well |
| Hearsay／Inference | Noun＋らしい | 先生らしい | Apparently a teacher／seems to be a teacher |
| Typical characteristic | Noun＋らしい | 子どもらしい | Childlike／typical of a child |
| Adverbial form | Noun＋らしく | 自分らしく働く | Work in a way that feels true to oneself |
| Negative form | Noun＋らしくない | 彼らしくない | Unlike him／not his usual style |
How Do You Interpret “Noun＋らしい”? Identity Inference vs. Typical Characteristics
When a noun is followed directly by “らしい,” the surface form can look exactly the same in both uses, so the structure alone is not enough to determine the meaning.
“彼は先生らしい” usually concerns the person’s identity and means something like “Apparently he is a teacher” or “It seems he is a teacher.” By contrast, “先生らしい話し方” uses “先生” as a typical standard and means that the way of speaking seems teacher-like.
- Example: あの人は学校の先生らしいです。
Kana: あのひとはがっこうのせんせいらしいです。
Translation: Apparently, that person is a school teacher.
The sentence conveys indirect information about the person’s identity, so this is the hearsay or inference use. - Example: 先生らしい落ち着いた話し方ですね。
Kana: せんせいらしいおちついたはなしかたですね。
Translation: That is a calm, teacher-like way of speaking.
“先生” is not being presented as identity information. It is being used as the standard for describing the typical characteristics of the “話し方.”
Why Can “学生らしい” Mean Either “Apparently a Student” or “Very Student-Like”?
“Noun＋らしい” is the easiest part of “らしい” to misinterpret because the hearsay or inference use and the typicality use can look identical.
When “彼は学生らしい” appears by itself, it is more likely to be understood as “Apparently he is a student” or “It seems he is a student.” In expressions such as “学生らしい服装” and “学生らしい生活,” however, “学生らしい” directly modifies the following noun, making it much clearer that the meaning is “clothing or a lifestyle typical of a student.”
A useful first check is whether a noun follows “らしい.” In the pattern “Nらしい＋noun,” the typicality meaning is usually obvious. When “Nらしい” appears at the end of a sentence, context becomes more important.
- Example: あの人は大学生らしいです。
Kana: あのひとはだいがくせいらしいです。
Translation: Apparently, that person is a university student.
The sentence concerns the person’s actual identity, so this is the hearsay or inference use. - Example: 大学生らしい自由な服装ですね。
Kana: だいがくせいらしいじゆうなふくそうですね。
Translation: That is a relaxed style of clothing that feels very university-student-like.
“大学生らしい” modifies “服装,” indicating that the clothing matches the speaker’s image of university students. - Example: 今日は彼らしくないですね。
Kana: きょうはかれらしくないですね。
Translation: He is really not acting like himself today.
“彼らしくない” means that today’s behavior or condition does not match what the speaker normally expects from him.
Japanese “らしい” Uses: Inference, Typical Characteristics, and Consistent Personal Style
In actual reading, “らしい” can be organized into three common situations. The first is inferring something from indirect information. The second is describing typical characteristics associated with identity, age, or season. The third is using a particular person, place, or group as a standard for style. Grammatically, the second and third both belong to the typicality pattern “noun＋らしい.”
“らしい” Use ①｜Expressing Hearsay or Inference Based on Indirect Information
Sentence-final “らしい” often means that the speaker does not know something through direct confirmation, but has learned it through another person, the news, online information, or some other clue. It does not always need to be translated as “I heard that.” Depending on the context, “apparently,” “it seems,” or “it looks like” may better match the actual nuance.
This use is more reserved than stating something as a definite fact. Especially when information has not yet been formally confirmed, “らしい” allows the speaker to say that the available information points in a certain direction without presenting indirect information as certain.
- Example: 明日は朝から雪が降るらしいです。
Kana: あしたはあさからゆきがふるらしいです。
Translation: Apparently, it is going to snow from tomorrow morning.
The weather information may come from a forecast or another source, so the speaker does not present it as something personally confirmed. - Example: この美術館は月曜日が休館らしいですよ。
Kana: このびじゅつかんはげつようびがきゅうかんらしいですよ。
Translation: Apparently, this museum is closed on Mondays.
The information may have come from a website, a friend, or another indirect source, so the speaker leaves some room for it not having been personally rechecked. - Example: 山田さんは以前、京都に住んでいたらしいです。
Kana: やまださんはいぜん、きょうとにすんでいたらしいです。
Translation: Apparently, Mr. Yamada used to live in Kyoto.
The speaker did not personally witness this part of Yamada’s past but learned it through other information.
“らしい” Use ②｜Expressing Typical Characteristics of an Identity, Age Group, or Season
“Noun＋らしい” can mean “having characteristics typically associated with this noun.” Common examples include “子どもらしい,” “大人らしい,” “春らしい,” and “学生らしい.”
This use of “らしい” depends partly on the speaker’s existing image of a certain identity or season, so it is not a purely objective classification. For example, “大人らしい態度” usually refers to qualities such as calmness and responsibility that are commonly associated with adults, while “春らしい天気” often evokes warmth and a gentle seasonal atmosphere.
- Example: 子どもらしい素直な発想ですね。
Kana: こどもらしいすなおなはっそうですね。
Translation: That is such an open and straightforward idea, very typical of a child.
The sentence describes a quality that fits the typical image of a child. It is not judging whether the person is actually a child. - Example: 今日は春らしい暖かさですね。
Kana: きょうははるらしいあたたかさですね。
Translation: Today’s warmth really feels like spring.
The temperature matches the speaker’s image of spring, so the typicality use of “らしい” is used. - Example: 最後まで責任を持つのは、社会人らしい態度です。
Kana: さいごまでせきにんをもつのは、しゃかいじんらしいたいどです。
Translation: Taking responsibility through to the end is an attitude expected of a working adult.
“社会人らしい” reflects expectations about how a working adult should behave.
“らしい” Use ③｜Expressing Someone’s, Somewhere’s, or a Group’s Consistent Style
Expressions such as “彼らしい答え,” “京都らしい町並み,” and “このチームらしい戦い方” also use “noun＋らしい.” The difference from the previous use is mainly the perspective: rather than describing a general social category, the sentence uses the accumulated impression of a particular person, place, or group as the standard.
“彼らしい” is therefore closer to “that is so like him” than simply “human-like.” The speaker usually already knows how that person tends to behave and can therefore judge that a particular answer or action fits their established style.
- Example: 最後まであきらめないのは、彼らしい選択です。
Kana: さいごまであきらめないのは、かれらしいせんたくです。
Translation: Choosing not to give up until the end is very typical of him.
The judgment comes from what the speaker already knows about this person, so “彼らしい” expresses a consistent personal style. - Example: 京都らしい落ち着いた町並みが残っています。
Kana: きょうとらしいおちついたまちなみがのこっています。
Translation: Calm streetscapes that feel distinctly Kyoto-like still remain.
“京都” becomes the stylistic standard, and the speaker judges that the scenery matches the typical image of Kyoto. - Example: 最後まで攻め続ける、このチームらしい試合でした。
Kana: さいごまでせめつづける、このチームらしいしあいでした。
Translation: They kept attacking until the very end—it was a match that really reflected this team’s style.
The way the game was played matched the team’s usual characteristics, so “チームらしい” is used.
What’s the Difference Between Japanese “らしい,” “そうだ,” “ようだ,” “みたいだ,” and “っぽい”?
“らしい” is easily confused with “そうだ,” “ようだ,” “みたいだ,” and “っぽい” because all of them may be translated into English with expressions such as “apparently,” “seems,” “looks like,” or “-like.” The real distinction depends on the source of information and whether the sentence is making an inference, relaying information, or describing appearance and typical characteristics.
| Pattern | Main Source of Judgment | Common Meaning | Example |
|---|---|---|---|
| “〜らしい” | Indirect information／typical impression | Apparently, it seems; typical of… | 雨が降るらしい／春らしい |
| Hearsay “〜そうだ” | Clearly heard information | I heard that, reportedly | 雨が降るそうだ |
| “〜ようだ” | Observation, evidence, reasoning | It seems, apparently | 雨が降ったようだ |
| “〜みたいだ” | Observation, judgment | It looks like, seems like | 雨が降ったみたい |
| “〜っぽい” | Appearance, tendency, impression | Kind of…, prone to… | 子どもっぽい |
Difference Between “らしい” and Hearsay “そうだ”: Indirect Judgment vs. Direct Relay
Hearsay “そうだ” primarily functions to pass along information obtained from somewhere else. “らしい” can also convey information, but it more easily includes the speaker’s own judgment based on indirect information, so the original source is not always as clearly foregrounded.
When a source is explicitly mentioned through expressions such as “ニュースによると” or “先生の話では,” “そうだ” is very natural. In casual conversation about information that has not yet been confirmed, “らしい” is also extremely common.
- Example: ニュースによると、来月から料金が上がるそうです。
Kana: ニュースによると、らいげつからりょうきんがあがるそうです。
Translation: According to the news, prices are going up starting next month.
The source is explicitly identified, and the focus is on relaying what the news reported. - Example: 駅前の店、来月閉店するらしいよ。
Kana: えきまえのみせ、らいげつへいてんするらしいよ。
Translation: Apparently, that shop in front of the station is closing next month.
The source is not specifically stated. The tone is more like information picked up from what people have been saying.
Difference Between “らしい” and “ようだ”: Indirect Information vs. Inference from Evidence
“ようだ” is often used when the speaker reasons from something directly observed, known evidence, or an actual situation. “らしい” more often relies on indirect information. However, the two are not completely separate, and “らしい” can sometimes be used for inference based on information such as physical symptoms.
- Example: 地面が濡れている。さっき雨が降ったようだ。
Kana: じめんがぬれている。さっきあめがふったようだ。
Translation: The ground is wet. It looks like it rained earlier.
The visible evidence—the wet ground—is the basis for inferring that it rained. - Example: 天気予報では、午後から雨が降るらしい。
Kana: てんきよほうでは、ごごからあめがふるらしい。
Translation: According to the weather forecast, apparently it will start raining this afternoon.
The information comes from the forecast rather than from directly observing the sky.
Difference Between “Nらしい” and “Nのような”: Typical Characteristics vs. Simple Similarity
“Nらしい” means that something has characteristics naturally or typically associated with N. “Nのような” only requires something to resemble N. The subject itself does not have to be N, and no typicality is required.
For example, “子どもらしい笑顔” usually describes a child showing a smile with qualities typically associated with children. “子どものような笑顔,” on the other hand, could describe an adult whose smile resembles that of a child.
- Example: 子どもらしい無邪気な笑顔ですね。
Kana: こどもらしいむじゃきなえがおですね。
Translation: That is such an innocent, childlike smile.
The focus is on qualities that fit the typical image of a child. - Example: 彼は子どものような笑顔を見せた。
Kana: かれはこどものようなえがおをみせた。
Translation: He showed a smile like a child’s.
The subject does not need to be a child. The sentence simply makes a comparison based on resemblance.
Difference Between “Nらしい” and “Nっぽい”: Typical Characteristics vs. Having a Certain Impression
“Nらしい” usually means that something fits the natural or typical qualities associated with a person, identity, or thing. “Nっぽい” is more conversational and simply indicates a tendency, appearance, or impression. It can also carry a negative evaluation.
“子どもらしい” can positively describe natural innocence or spontaneity, while “子どもっぽい” easily takes on the meaning “childish” or “immature.”
- Example: 子どもらしい自由な発想です。
Kana: こどもらしいじゆうなはっそうです。
Translation: It is a wonderfully free, childlike way of thinking.
The sentence treats imagination and freedom as natural characteristics associated with children, giving the expression a neutral or positive tone. - Example: その言い方は少し子どもっぽいです。
Kana: そのいいかたはすこしこどもっぽいです。
Translation: That way of saying it sounds a little childish.
“っぽい” only indicates that something gives off a certain impression, and here it also carries the negative evaluation of being somewhat immature.
Japanese “らしい” in Travel, the Workplace, and Everyday Conversation
“らしい” is extremely practical in everyday Japanese because people often speak before they have personally confirmed every piece of information. Hearing that a shop is closed while traveling, a friend mentioning that it will rain tomorrow, or coworkers discussing a plan that has not yet been officially announced can all lead to the hearsay or inference use of “らしい.”
At the same time, expressions such as “春らしい,” “京都らしい,” and “彼らしい” are equally common in everyday impressions. These sentences are not concerned with verifying facts. They describe how something feels, so seeing “らしい” should not automatically trigger the translation “I heard that.”
Scenario ①｜Checking Whether a Shop Is Open While Traveling
A：この店、今日は休みですか。
このみせ、きょうはやすみですか。
Is this shop closed today?
B：ネットで見たんですが、今日は休みらしいです。
ネットでみたんですが、きょうはやすみらしいです。
I saw it online, and apparently they are closed today.
📌 Grammar Point: “休みらしい” indicates that the speaker is currently making a judgment based on online information rather than presenting something that has been personally confirmed on site.
Scenario ②｜Describing a Coworker’s Usual Work Style
A：この資料、すごく佐藤さんらしいですね。
このしりょう、すごくさとうさんらしいですね。
This document really feels like something Sato would make.
B：細かいところまで整理されていますね。
こまかいところまでせいりされていますね。
Even the smallest details are carefully organized.
📌 Grammar Point: “佐藤さんらしい” means that the way the document is presented matches the speaker’s previous impression of Sato’s work style. It does not mean “Apparently this is Mr. Sato.”
Scenario ③｜Talking About Seasonal Weather
A：今日は暖かいですね。
きょうはあたたかいですね。
It is warm today, isn’t it?
B：やっと春らしい天気になりましたね。
やっとはるらしいてんきになりましたね。
It finally feels like spring weather.
📌 Grammar Point: “春らしい” describes weather that matches the typical impression of spring. It has nothing to do with hearsay or making a prediction about whether spring has arrived.
Cultural Notes:
- “男らしい” and “女らしい” are also typicality uses of “noun＋らしい,” but these expressions can easily carry gender stereotypes. In actual descriptions of people, using concrete characteristics such as “落ち着いている” or “行動力がある” is often clearer than applying broad gender expectations.
- “自分らしい” and “彼らしい” are extremely common in modern Japanese because the preceding noun does not have to refer to a social category. It can represent an individual’s consistent personality and style. “自分らしく働く” means working in a way that feels true to oneself.
- Hearsay “らしい” does not mean the information is necessarily unreliable. Official forecasts and news reports can also serve as information sources for “らしい.” The main distinction is that the speaker positions the information as indirectly obtained rather than personally verified.
How Does Japanese “らしい” Compare with Korean “-다고 하다,” “-(으)ㄴ/는 모양이다,” and “-답다”?
Japanese “らしい” covers both judgment based on indirect information and typical characteristics, so there is no single Korean grammar pattern that matches every use.
For reported information, Korean “-다고 하다” is a useful comparison. When “らしい” means “it seems” based on indirect clues or available evidence, “-(으)ㄴ/는 모양이다” can also be close. For the typicality use of “noun＋らしい,” Korean “noun＋답다” is especially similar.
◆ Similar Grammar ①: Korean “-다고 하다”
“-다고 하다” is used to report information heard from another person, the news, an announcement, or another source. Like the hearsay use of Japanese “らしい,” it indicates that the information was not directly confirmed by the speaker. However, “-다고 하다” has a stronger reporting function, often emphasizing that “someone said this” or “this information was received,” and it is also close to Japanese hearsay “〜そうだ.”
- Example: 내일 비가 온다고 해요.
Romanization: nae-il bi-ga on-da-go hae-yo.
Translation: I heard that it will rain tomorrow.
The sentence relays information obtained from a weather forecast or another source. It is close to Japanese “明日は雨が降るらしいです,” with the focus on the information currently available. - Example: 민지 씨는 다음 달에 일본으로 이사 간다고 해요.
Romanization: min-ji ssi-neun da-eum dal-e il-bon-eu-ro i-sa gan-da-go hae-yo.
Translation: I heard that Minji is moving to Japan next month.
The information about moving comes from Minji or another person, so “-다고 하다” is used to report it. In Japanese, depending on context, this could be “ミンジさんは来月、日本に引っ越すらしいです.” - Example: 이 식당은 주말에 예약이 필요하다고 해요.
Romanization: i sik-dang-eun ju-mal-e ye-yag-i pil-yo-ha-da-go hae-yo.
Translation: I heard that reservations are required at this restaurant on weekends.
The sentence reports information from the restaurant’s website, a friend, or another source rather than inferring it from the situation on site. For that reason, “-다고 하다” is more appropriate than “모양이다.”
◆ Similar Grammar ②: Korean “-(으)ㄴ/는 모양이다”
“-(으)ㄴ/는 모양이다” expresses an inference based on the current situation, visible evidence, or information presently available. It is often translated as “it seems,” “apparently,” or “it looks like.” This overlaps with some inferential uses of Japanese “らしい,” although Korean “모양이다” more strongly suggests that there is some specific clue serving as the basis of the judgment.
- Example: 사람이 없는 걸 보니 오늘은 쉬는 모양이에요.
Romanization: sa-ram-i eom-neun geol bo-ni o-neul-eun swi-neun mo-yang-i-e-yo.
Translation: There is nobody here, so it looks like they are closed today.
The absence of customers or staff provides the clue used to infer that the shop is closed. Depending on the Japanese context, this could also be expressed as “今日は休みらしいです.” - Example: 불이 꺼져 있는 걸 보니 벌써 문을 닫은 모양이에요.
Romanization: bul-i kkeo-jyeo it-neun geol bo-ni beol-sseo mun-eul da-deun mo-yang-i-e-yo.
Translation: The lights are off, so it looks like they have already closed.
The fact that the lights are off is visible evidence, and the speaker uses that clue to infer that the shop has closed. This is a very typical use of “모양이다.” - Example: 기침을 계속하는 걸 보니 감기에 걸린 모양이에요.
Romanization: gi-chim-eul gye-sok-ha-neun geol bo-ni gam-gi-e geol-lin mo-yang-i-e-yo.
Translation: They keep coughing, so it looks like they have a cold.
The speaker infers that the person may have a cold from the observable symptom of persistent coughing rather than from a confirmed diagnosis. This clue-based inference is a characteristic use of “모양이다.”
◆ Similar Grammar ③: Korean “-답다”
“Noun＋답다” means having the characteristics considered typical, appropriate, or expected of that noun, making it especially close to the typicality use of Japanese “noun＋らしい.” For example, “아이답다” means childlike or typical of a child, while “봄답다” means having the qualities typically associated with spring. However, “-답다” can sometimes also imply behavior considered appropriate for a particular role or identity, so the exact nuance still depends on the noun and context.
- Example: 아이답게 솔직한 생각이에요.
Romanization: a-i-dap-ge sol-jik-han saeng-gak-i-e-yo.
Translation: It is such a straightforward, childlike way of thinking.
“아이답게” means that this direct and honest thought matches the typical image of a child, making it very close to Japanese “子どもらしい素直な考えです.” - Example: 오늘은 봄답게 날씨가 따뜻해요.
Romanization: o-neul-eun bom-dap-ge nal-ssi-ga tta-tteut-hae-yo.
Translation: The weather is warm today—it really feels like spring.
“봄답게” uses spring as the standard, indicating that today’s temperature matches the typical impression of spring. This is close to Japanese “今日は春らしい暖かさです.” - Example: 그 사람다운 선택이네요.
Romanization: geu sa-ram-da-un seon-taeg-i-ne-yo.
Translation: That choice is really typical of that person.
Here, the expression is not describing a general identity category. It uses the specific person’s usual personality and behavior as the standard. The nuance is very close to Japanese “彼らしい選択ですね,” with both expressions indicating consistency with someone’s established style.
◆ Core Difference from Japanese “らしい”:
Japanese “らしい” can be used both for inference based on indirect information and for typicality. “雨が降るらしい” concerns an information-based judgment, while “春らしい天気” describes typical characteristics.
Korean usually chooses different forms depending on the function of the sentence. Simple reported information commonly uses “-다고 하다.” Inference based on clues can use “-(으)ㄴ/는 모양이다.” Typical characteristics of a person or thing can be expressed with “-답다.”
For this reason, rather than assigning one fixed Korean equivalent to “らしい,” it is more accurate to first determine whether the sentence is reporting information, making an inference from clues, or describing something as “typical of” a person or thing.
The difficult part of “らしい” is not that it has many meanings, but that two different functions can sometimes look exactly the same. “彼は学生らしい” and “学生らしい服装” both contain “学生らしい.” The first may convey information about someone’s identity, while the second describes the typical impression created by the clothing.
When you see sentence-final “らしい,” first ask where the information came from. When you see expressions such as “春らしい天気” or “彼らしい選択” modifying a noun, shift the focus to “what image or characteristic does this fit?” Understanding “らしい” this way is much more precise than translating every occurrence as “I heard that.”
FAQ
“らしい” can mainly be organized into two broad categories. The first expresses hearsay or inference based on indirect information and is often translated as “apparently,” “I heard that,” or “it seems.” The second is “noun＋らしい,” which describes typical characteristics, as in “春らしい,” “子どもらしい,” and “彼らしい.”
Both can convey indirectly obtained information, but “そうだ” is more like directly relaying what was heard, while “らしい” more easily carries the nuance of a judgment formed from indirect information. When the source is clearly stated, expressions such as “ニュースによると〜そうだ” are common. For general information that has not yet been confirmed, “〜らしい” appears very frequently.
Grammatically, no. “彼らしい答え” still belongs to the typicality use of “noun＋らしい.” The difference is that the noun is not a general category such as “child,” “spring,” or “student,” but a particular person. The meaning therefore becomes “an answer very typical of him” or “an answer that fits his usual style.”
“子どもらしい” means that something fits the natural or typical characteristics associated with children and can be used neutrally or positively. “子どもっぽい” simply means that something gives a childlike impression and can easily carry the negative meaning “childish” or “immature.” For example, “子どもらしい発想” can be a compliment, while “子どもっぽい態度” usually is not.
You need to look at the function of the sentence and the surrounding context. “彼は学生らしい” usually concerns identity and is closer to “Apparently, he is a student.” “学生らしい服装,” by contrast, clearly modifies “服装” and means clothing that matches the typical image of a student. When you see “Nらしい＋noun,” the typicality meaning is generally easier to identify.