Difference between てもいい and ていい?


> 寝ていい？

I've learned that to ask permission for doing something, you needed to use
～てもいい but the more I read japanese, the more I come across ～ていい. What is the
difference ? Is the latter a colloquial version of ～てもいい ?




There is a difference even though it might be fairly subtle. **_The difference
is one of nuance and probability; It has little to nothing to do with
formality/colloquiality_**.

> 「Verb in Te-Form + いい？」

The speaker would tend to possess a firm desire to perform the action and he
is seeking permission to do so.

Upon receiving the permission, therefore, there is a high chance that he would
actually take the action.

> 「Verb in Te-Form + **も** + いい？」

The speaker is surely considering taking the action for which he is seeking
permission, but his desire to actually perform the said action would often
tend to be less firm than that of the person who does **_not_** use the 「も」.

Upon receiving the permission, there is a good chance that this person
(speaker) might actually opt to take a completely different action.

For this reason, adding a 「も」 makes both the question and the questioner sound
less pushy or self-assertive.




There is a difference even though it might be fairly subtle. **_The difference
is one of nuance and probability; It has little to nothing to do with
formality/colloquiality_**.

> 「Verb in Te-Form + いい？」

The speaker would tend to possess a firm desire to perform the action and he
is seeking permission to do so.

Upon receiving the permission, therefore, there is a high chance that he would
actually take the action.

> 「Verb in Te-Form + **も** + いい？」

The speaker is surely considering taking the action for which he is seeking
permission, but his desire to actually perform the said action would often
tend to be less firm than that of the person who does **_not_** use the 「も」.

Upon receiving the permission, there is a good chance that this person
(speaker) might actually opt to take a completely different action.

For this reason, adding a 「も」 makes both the question and the questioner sound
less pushy or self-assertive.

