Planimeters

Part of speech: noun

Definitions

1. An instrument used for measuring the area of a two-dimensional shape by tracing its perimeter
2. a device that calculates enclosed surfaces through manual or mechanical means
3. a tool employed in various fields such as surveying and cartography to determine surface areas accurately

Etymology: "Planimeters" is the plural of "planimeter", a device for finding the area of a flat figure by tracing its outline. The name is a plain compound: "plani-", from Latin "planus" meaning flat or level, joined to "-meter", from Greek "métron", measure. Together they describe exactly what the instrument does, measuring flatness, or flat area, in the way a thermometer measures heat. The second half of the word has travelled a long way. The Greek "métron" passed into French as "-mètre", and English took the element as "-meter", so the same ending appears in "barometer", "speedometer" and "kilometer". Each of these pairs a measured quantity with the Greek root for measure, and "planimeter" follows that pattern exactly, applying it to surface area.