(aviation) An instrument that displays an aircraft's current airspeed.

(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.

plural of ordinal indicator

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

plural of pH indicator

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

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 leading indicator