ichidan verb
can wear; be able to wear; fit into
Potential form of 着る (to wear). Used for clothing, accessories, or anything worn on the body. The 'fit into' nuance appears when the item is physically possible to put on, often regarding size.
このジャケット、まだ着れるよ。
I can still wear this jacket.
サイズが小さくて着れなかった。
It was too small and I couldn't fit into it.
着る is the base verb meaning 'to wear (on the upper body or whole body)'. 着れる is its potential form, meaning 'can wear' or 'is wearable'.
着られる is the traditional potential form of 着る, but 着れる is now widely accepted as the standard potential form in modern Japanese. 着られる can also be the passive or honorific form, so 着れる avoids ambiguity.
Potential form of 着る (to wear), formed by replacing the -ru ending with -reru. This is a regular potential formation for ichidan verbs.