Having only one colour. / (photography) Representing colours with shades of gray.

a believer in, or advocate of, monotheism

(informal) dihydrogen monoxide (water (H₂O), but not hydrogen peroxide (H₂O₂) or the hydroxyl radical (-OH))

(inorganic chemistry, usually humorous) H₂O, water.

(inorganic chemistry) nitrous oxide

Nitric oxide.

A person who is obsessed with a single thing, to the exclusion of other concerns.

Focused on one thing above all others.

Alternative spelling of monopolize

A scholarly book or a treatise on a single subject or a group of related subjects, usually written by one person.