Etimology
From Middle English tonyght, to niȝt, from Old English tō niht.
adverb
tonight (not comparable)
During the night following the current day; during the evening of today.
(obsolete) Last night.
Examples
I want to party tonight!
I had a wonderful time with you tonight.
Besides, I met Lord Bigot and Lord Salisbury,With eyes as red as new-enkindled fire,And others more, going to seek the graveOf Arthur, whom they say is killed to-nightOn your suggestion.
I dreamt tonight that I did feast with Caesar,And things unluckily charge my fantasy;
noun
tonight (usually uncountable, plural tonights)
The nighttime of the current day or date; this night.
Examples
Tonight is the night.
I have high hopes for tonight.