〜らしい (typical of)
typical of, just as (X) should be
Noun + らしい / らしく / らしくない
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At N4, らしい meant "apparently" (hearsay). After a noun, it has a second meaning: "having the qualities that X should have". 今日は春らしい暖かい日だ, "today is a warm, truly spring-like day".
It's usually a compliment: 子どもらしい, "just like a kid should be"; 学生らしい, "fitting for a student".
The negative is a gentle criticism: 君らしくないね, "that's not like you".
As an adverb, it's らしく: 子どもは子どもらしく遊ぶのが一番だ, "kids should play like kids".
Compare っぽい, which is "-ish" and often negative: 子どもっぽい is "childish". Context usually shows which らしい is meant: after a noun describing character, it's "typical of".
Examples
今日は春らしい暖かい日だ。
Today is a warm, truly spring-like day.
そんなことを言うなんて、君らしくないね。
It's not like you to say something like that.
彼女は学生らしい服を着ている。
She's wearing clothes that are just right for a student.
子どもは子どもらしく遊ぶのが一番だ。
It's best for kids to play like kids.
久しぶりに夏らしい天気になった。
For the first time in a while, it feels like proper summer weather.