てもいい details

write + (and…) + may do

kaite mo ii

may do; it's okay to do

meaning: may write

このパソコンは誰だれでも自由じゆうに使っつかってもいい。

kono pasokon wa dare demo jiyuu ni tsukatte mo ii.

Anyone may use this computer. neutral

この傘かさ、借かりてもいい？

kono kasa, karite mo ii?

Can I borrow this umbrella? casual

contraction
formal
formal
past
polite
polite question

Examples

may do; it's okay to do — asking or granting permission

このパソコンは誰だれでも自由じゆうに使つかってもいい。

kono pasokon wa dare demo jiyuu ni tsukattemoii.

Anyone may use this computer. neutral

この傘かさ、借かりてもいい？

kono kasa, karite mo ii?

Can I borrow this umbrella? casual

写真しゃしんを撮とってもいいですか。

shashin o totte mo ii desu ka.

May I take a photo? neutral

こちらの資料しりょうは持もち帰かえってもよろしいでしょうか。

kochira no shiryou wa mochikaette mo yoroshii deshou ka.

Would it be alright if I took these materials home? formal

Formation

{V-te}もいいattaches to て-form

Variant notes

ていい — も dropped in casual speech — 入[はい]っていい？
てもかまわない — literally "(I) don't mind if you do" — cooler, more detached than てもいい
てもよろしいでしょうか — keigo permission request toward superiors and customers

Notes

Granting permission presupposes the authority to grant it — answering a superior's request with てもいいよ sounds off; permission flows down, requests flow up.

Related patterns

Similar

なくてもいい
Matched pair sharing the もいい shell — てもいい permits DOING, なくてもいい permits NOT doing; each grants latitude over the same act from the opposite side.

Opposite

てはいけないprohibition-vs-permission
Same て-frame one kana apart — も grants ("may do"), は forbids ("must not do").

Lookalikes

ても
ても alone concedes ("even if"); adding いい turns the concession into permission — the shared ても opening invites misparsing mid-sentence.

Same meaning

may do; it's okay to

Pattern	Attaches to
`temo-kamawanai` (planned)	—