yes

Yes is defined as an affirmative answer that indicates acceptance, or delight, or it can be used to attract attention or to ask a question.

(interjection)

When someone asks you if you are ready to go and you are ready to go, this is an example of a time when you might say "yes."
When someone asks if you agree with a statement they made, this is an example of a time when you might say "yes, I do."
When you want to ask someone if they agree with your opinion on a sports game, this is an example of a time when you might say 'Good game, yes?"
When you score a goal and are really excited, this is an example of a time when you might shout "yes!"

See yes in Webster's New World College Dictionary

adverb

aye; yea; it is so: the opposite of no, used to express agreement, consent, affirmation, or confirmation
not only that, but more; moreover [ready, yes, eager to help]

Origin: ME < OE gese, yes, prob. < gea, yea + si, be it so, 3d pers. sing., pres. subj., of beon, to be: see be

interjection

it is so; aye; yea: the opposite of no
Informal good, that's it, I've got it, etc.: spoken emphatically in expressing satisfaction, agreement, pleasure, etc.
what is it? do you wish to say (or add) something?: used in inquiry
is it so?: used in conversation to express polite interest

noun pl. yeses