Isn't there no difference between yeah, yes and yah

Question

“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.)

Answer 1

'Yes' can be considered the baseline - I can't think of any context in which using it would be inappropriate. (It might come across as slightly over-formal on some occasions, but more likely no-one would pay attention to it) Any official/formal speech will most likely use 'yes', as will almost all written usage.

'Yeah' is an informal equivalent to 'yes'. In casual conversation you are more likely to hear 'yeah' than 'yes' unless the speakers are making a deliberate effort to be precise with their speech (the reason that 'yes' can potentially sound overly-formal). On the other hand, a written 'yeah' will generally only be used when writing dialogue.

'Yah' would be 'yeah' spoken in a different accent. I would personally associate it either with a non-native speaker (the German accent in particular), or with native speakers who are uneducated/unsophisticated.

Answer 2

"Yes" is proper and correct, while "yeah" is slang. When "yah" is spoken it is typically heard as an accented version of "yes."

Typically one will say "yes" to be concise, or to convey respect or formality, and acknowledge that the question is itself important.

"Yeah" is informal, and is an acceptable response when the speaker and listener are friends or peers, or the question asked does not require a precise answer.

Answer 3

Yes is a formal word.

Yeah and Yah are informal.

As an aside "Yeah, yeah" said sarcastically, can mean "no".