“Are you coming with us?” “Yeah, I'm coming.” (Merriam-Webster's Learner's)
In my tongue, for saying ‘yes (Korean yes),’ I could say ‘ye [je̞]’ or ‘ne [ne].’ Korean dictionaries say there’s no difference, not even some subtle nuance difference at all between the two - there’s my favourite but it would be just mine on the dictionaries. However if someone would say ‘yeah [jɛə]’ for Korean yes, it would be heard as a kind of contorted sound by gangsters or whatever. So whenever some of those who learned English from private English teaching classes make the sound for English yes, I flinch, even get sick: I don’t know if the native teachers really make the same sound.
If the sound were ‘yah [yɑ:],’ - in fact, some Korean local accent uses [ya] for Korean yes, but if the users are not the accent users (we don't differentiate /yɑ/ from /ya/) - it would, I’m sorry, piss the hearers off.
Do you use ‘yeah’ and ‘yes’ with no nuance difference at all? Can you tell me about these three: yeah, yes, yah? (If any, I also want to hear about them other than aforementioned.)