'numerous' and 'many'

They mean the same thing, but numerous is more formal.

Hi contrex,
thank you. How about numberless and numerous?

"Numberless" means "too many to count" and usually means "very numerous" or "very many" or even "infinite".

Can I say that ants are numberless on the floor?

Yes. This word literally means "infinite" or "literally uncountable" but is often used in a poetic/figurative way to mean "impressively many". You could, in theory, count the ants on the floor if you had time, but nobody does. Numberless flies buzzed around the rotten meat; numberless stars shone in the clear night sky. Maybe we wish to say the quantity of something is unknowable: it is from numberless diverse acts of courage and belief that human history is shaped.

Good morning,
Thank you very much for your explanation.