(chemistry) any substance used to classify another, often by changing colour

(aviation, UK, military) An instrument that displays attitude of an aircraft in pitch and roll.

The imperfect tense in the indicative mood

(grammar) The present tense in the indicative mood.

A sign adjacent to a numeral denoting that it is an ordinal number, rather than a cardinal number.

A float used by anglers to tell when a fish has taken the bait

(algebra, of a group) Such that each of its nontrivial, finitely generated subgroups maps homomorphically onto ℤ.

Any device for comparing a physical property of two objects, or an object with a standard.

A phenomenon that generally occurs in advance of a more important phenomenon, aiding in its prediction.

plural of price index