indicator

The general sense the others narrow from: Late Latin indicātor, "one who points out", from indicō, "point out". Besides any telling sign, it names a physical display. Railway Magazine wrote in 1954 of the arrival indicators at Euston, and the old Earl's Court indicators lit an arrow beside a station name to show where the next train was bound. Gauges, chemicals and flashing car lights are narrower uses of the same idea.

Economists sort these by timing. A leading indicator moves before the business cycle turns, a lagging one confirms the turn afterward, and a coincident one moves along with it. Employment figures, inflation and industrial output can each play these roles. In news prose the word is often plural and active: indicators point to, signal or suggest a slowdown.

Drivers in the UK, Ireland, Australia, New Zealand and South Africa use this name for a car's turn signal. Americans say turn signal or directional instead. Blinker is the casual word, direction indicator is the fuller name, and trafficator is another. A line like "put your indicator on" therefore marks a speaker as British or Commonwealth to American ears.

Chemistry relies on color to signal change. Litmus, phenolphthalein and methyl orange each shift color over a characteristic transition range, usually of pH. That range is why the choice matters: in an acid–base titration, the chemist picks an indicator whose change falls at the expected endpoint. The word is freely countable here, and each indicator suits a different range.

Ecologists read living things as instruments. Absence and abundance count as much as presence: a stream that loses its mayfly larvae is reporting something too. The value lies in indirect measurement, because the organism reveals habitat quality, pollution or ecosystem change without anyone testing the water or air directly. The word usually takes of, as in an indicator of clean water.

Here the word moves from the whole instrument to the part you actually watch. Because the gauge itself and its needle share the name, context does the sorting: an indicator that swings, flickers or sticks at zero is the needle, while one that is installed or replaced is usually the whole device.

Solvers of cryptic crosswords use the word for a signpost hidden inside a clue. It usually comes with its kind attached: anagram, container, reversal or deletion indicator. 'Wild' tells you to rearrange danger, and 'surrounded' tells you to put letters inside others. The trap is that one word can serve several devices: 'round' may signal containment or reversal, and 'without' may signal containment or deletion.

The bird's name takes the pointing sense literally. Honeyguides lead people and honey badgers to wild bee colonies, then feed on the wax and larvae left exposed. Capitalized, Indicator is the scientific genus that covers these African and Asian birds. Lowercase, it names a single bird.