I don't have much time.

A large amount of something, often used with uncountable nouns.
There isn't much food left.
She doesn't have much money.
We need much more help.
much time
much information
much effort
a lot of
plenty of
numerous
Much is unknown about the topic.

A large amount or degree of something, used without a noun.
Much has changed since then.
Much remains to be done.
Much is at stake.
much more
much less
much better
a lot
plenty
many
I like pizza much more than salad.

To a great extent or degree.
I enjoy reading much more than watching TV.
She runs much faster than her brother.
They travel much more often than we do.
much better
much more
much less
far
significantly
considerably
He is much taller than his brother.

Great in quantity or degree.
She has much homework to do.
There is much to learn in this class.
He has much respect for his teacher.
much time
much effort
much attention
ample
plenty
substantial