Likeness and hearsay with みたい, らしい, ぽい, and そう

There are many ways in Japanese to say "X resembles Y" or "X looks like Y".

One of them, is the な adjective suffix みたい. It looks like the たい form of 見る -> 見たい, however in modern Japanese this is considered a completely separate thing and should not be confused.

みたい (it is always written in kana and should never be written as 見たい) is a な-adjective and conjugates like one. It means “seems”.

あの人、日本人みたい
That person, it seems like he’s Japanese / He seems Japanese

ヒーローみたいな人
Person that resembles a hero

While みたい is for all intents and purposes a な adjective, when used adverbially it sometimes conjugates like an い adjective. This is seen as casual/slang, but you’ll see it often enough in Japanese media that it is good to be aware of it.

子供みたいにブランコに乗っている
子供みたくブランコに乗っている
He was on the swing like a child

Both of these examples are valid, but the former is more proper.

らしい is an auxiliary adjective that attaches to nouns or verbs/adjectives and says that something factually "seems so" based on circumstance. らしい is appropriate for things that would translate to "seems X", rather than "Xish".

日本人らしい名前。
A name that seems Japanese.

You might also see らしい used to mean “I heard that”, used to convey hearsay or information obtained from third parties.

出発は明日の昼頃になるらしい。
I heard that the departure will be tomorrow at around noon.

ぽい/っぽい is a suffix い adjective that says that something subjectively "seems so" based on appearance or stereotypical properties. It translates well as "Xish" or "X-like". It sounds casual.

今、僕の名前、女っぽいって思ったでしょ？
You just thought my name sounded feminine-ish, right? (lit: “female-ish” or “woman-ish”)

There are two separate constructions of the auxiliary suffix そう.

The first one attaches to the masu stem of a verb or adjective, and it means “seems like”. It is used to describe things from a subjective impression or perspective, often from physical appearances. そう turns whatever it attaches to into a な adjective.

おいしそうなスープです。
A delicious-looking soup.

The other そう attaches to the complete form of the word before it, so for な adjectives and nouns it becomes だそう. This usage means “I heard that” and it is similar to the hearsay usage of らしい we saw earlier. It feels a bit more formal.

2000人以上が死んだそうです。
I heard that over 2000 people died.