I have to wait until I'm 21 years old to get the money my grandma left me.
How long are you going to wait for an answer? Until 8pm? Until midnight? Until next Tuesday? No, "Until." is not a sentence.
'Is until tomorrow' is a fragment, because it has no real subject. You can make it a sentence: What Is until tomorrow?
It is an imperative sentence.
"Until" is the preposition in the sentence "They played until 11 o'clock." It shows the relationship between the playing and the specific time.
"We could only stay out until 11 P.M."
Example sentence - They would want to wait until they sky looked white too.
I will wait until you are done cleaning your room
I play outside until it gets dark!
until you eat your vegetables
The verb in the sentence is "wait."
Waited
Don't come back until 5 pm.