Nihil - Nothing
Nil actum credens dum quid superesset agendum - Thinking nothing done, while anything was yet to do
Nil actum reputa si quid superest agendum - Don't consider that anything has been done if anything is left to be done. (Lucan)

Nil admirari

To admire nothing. (Horace)

Nil agit exemplum, litem quod lite resolvit - Not much worth is an example that solves one quarrel with another. (Horace)
Nil desperandum! - Never despair! (Horace)
Nil homini certum est - Nothing is certain for man. (Ovid)
Nil sine numine - Nothing without the Divine Will
Nill illigitimi carborundum - Do not let the bastards get you down
Nisi credideritis, non intelligetis - Unless you will have believed, you will not understand. (St. Augustine)