Similar word to yep:

affirmative, all right, amen, aye, beyond a doubt, by all means, certainly, definitely, even so, exactly, fine, gladly, good, good enough, granted, indubitably, just so, most assuredly, naturally, of course, okay, positively, precisely, sure thing, surely, true, undoubtedly, unquestionably, very well, willingly, without fail, yea, yep