Definition from Wiktionary, the free dictionary
Alternative forms 
From Old English tōniht.
tonight (plural tonights)
- The nighttime of the current day or date; this night.
- Tonight is the night.
- I have high hopes for tonight.
tonight (not comparable)
- During the night following the current day.
- I want to party tonight!
- I had a wonderful time with you tonight.
- Tonight is a great night for sangria!
- (obsolete) Last night.
- (Can we find and add a quotation of Shakespeare to this entry?)
during today's evening
during today's nighttime