Open English Wordnet
Nouns
(n)yesterdaythe day immediately before today“it was in yesterday's newspapers” (n)yesterdaythe recent past“yesterday's solutions are not good enough”,
“we shared many yesterdays” Adverbs
(r)yesterdayon the day preceding today“yesterday the weather was beautiful” (r)yesterdayin the recent past; only a short time ago“I was not born yesterday!”