(astronomy) A catalogue number used to identify any one of more than one hundred galaxies, nebulae, and other deep-sky objects visible in the night sky; the designation formed by the surname Messier or letter M being prepended to the number, as in Messier 31 or M31 (the Andromeda Galaxy).

(chemistry) the number of molecules that are associated together to form a micelle

plural of deficient number

(usually used attributively) A simple drawing exercise, intended especially for children, consisting of a line drawing that divides the artwork into distinct spaces, the intended color of each indicated by a number and referenced from a key.

To complete such an exercise; to carry out such a technique by filling in each space with the appropriate color.

alternative form of color by number / (rare) plural of color by number

alternative form of color by number

A memorable mobile phone number.

(chemistry, physics) The number of atoms present in 12 grams of isotopically pure carbon-12, being 6.02214076 × 10²³. By definition, the number of elementary entities (atoms or molecules) comprising one mole of a given substance.

(informal) To damage; to treat harshly; to produce ill effects in.