There appears to be some disagreement over what function yes and no perform in the following sentences:
- Yes, you are right.
- No, you are mistaken.
According to ODO (yes, no), they are being used as exclamations which are presumably the same as interjections. Webster (yes, no) and Macmillan (yes, no), on the other hand, reckon that they are adverbs. Wiktionary (yes, no) chucks another spanner by stating that yes is being used as an adverb while no is being used as an interjection.
Wiktionary also links to a Wikipedia article on "yes and no" which seemingly disagrees with both options.
The words yes and no are not easily classified into any of the eight conventional parts of speech. Although sometimes classified as interjections, they do not qualify as such, and they are not adverbs. They are sometimes classified as a part of speech in their own right, sentence words, word sentences, or pro-sentences, although that category contains more than yes and no and not all linguists include them in their lists of sentence words. Sentences consisting solely of one of these two words are classified as minor sentences.
So, which, if anything, is it and why is opinion so divided?