may do; it's okay to do (permission)
Form: verb て-form + もいい. Same て-form conjugation as 〜てはいけない — get comfortable with one and the other comes for free.
Meaning: grants permission (you may) or asks for it (may I…?). Add か / ですか to ask; use as a statement to give.
Register variants:
- Casual drop of も: 座っていい？ can I sit? — very informal.
- Polite: 座ってもいいですか.
- Extra polite (asking a superior): 座ってもよろしいですか / 〜ても構いませんか would you mind if…?.
Negative side of the pair:
- Denying permission: 〜てはいけない you may not (see the [[〜てはいけない]] card).
- Saying you don't have to: 〜なくてもいい — 食べなくてもいい you don't have to eat it. Same もいい ending, negative stem.
Nuance: granting permission with 〜てもいいですよ can sound slightly condescending in the wrong context — like the speaker is allowing the listener. Between equals, どうぞ or 大丈夫だよ is often warmer.
Furigana is above every kanji; the pattern is already filled in.
ここに座ってもいいですか。
Is it okay if I sit here?
窓を開けてもいい？
Can I open the window?
この本を借りてもいいですよ。
You may borrow this book.