Etymology: < classical Latin -meter (in e.g. pentameter ) < ancient Greek -μετρος , (neuter) -μετρον (in e.g. πεντάμετρος , πεντάμετρον ) < μέτρον measure (see metre n.¹). Compare French -mètre (formations in which are found from 18th cent.).Almost all formations in the small set of words with this terminal element are first attested in ancient Greek or Hellenistic Greek and are found as loanwords in classical Latin or post-classical Latin. Earliest in English are dimeter n., hexameter n., pentameter n., and trimeter n., all dating from the 16th cent. (apart from an isolated occurrence of exametron in Chaucer); the latest (among which is the rare decameter n. at deca- comb. form 1) date from the early 19th cent.

Etymology: < Middle French, French -mètre (partly via post-classical Latin -meter, -metrum) < ancient Greek -μέτρον (in e.g. ὁδόμετρον : see odometer n.), use as second element of compound of μέτρον measure (see metre n.¹). Compare -imeter comb. form, -ometer comb. form (and see note below).The generation of scientific and technical terms containing this element appears to have originated in Middle French in the second half of the 16th century. The seminal item was perhaps altimètre (originally an adjective designating a geometrical instrument, probably borrowed from or formed after post-classical Latin altimeter : see altimeter n.). 16th-cent. formations in Middle French include micromètre (see micrometer n.) and graphomètre (see graphometer n.). Words containing this terminal element are first attested in English in the 17th cent., the earliest significant example being thermometer n., modelled on the earlier French thermomètre ; the next is barometer n., an English formation (French baromètre is recorded almost contemporaneously). A relatively small number of others are first attested during the 17th cent., some (e.g. graphometer n., micrometer n., and pantometer n.) being formed after French models, others (e.g. holometer n., hydrometer n., and hygrometer n.) showing the emergence of the termination as a standard formative element in English. A much larger number of words with this element are first attested during the 18th century; a substantial proportion again being after French models (notable examples being chronometer n., manometer n., and odometer n.). In the early formations the ending is always appended to Greek noun stems or combining forms in -o . During the 18th cent. formations begin to appear in which the initial element could be of Latin or other origin (e.g. gravimeter n., velocimeter n.); this at first had the form of a Greek or Latin combining element. From the 19th cent. onwards appear formations without assimilation of the first element to the form of a classical combining form (e.g. litrameter n., viameter n., voltameter n.), formations with (partial or complete) initial elements of English origin (e.g. ammeter n., decremeter n.), and formations in -ometer (see -ometer comb. form) and -imeter (see -imeter comb. form) with non-classical first elements. Since the early 19th cent. noun compounds with meter n.³ as the second element have become common (compare meter n.³ 1b). Formations in which -meter , without a medial connecting vowel, is compounded with an English word (e.g. voltmeter n.) are probably to be classified with these rather than treated as examples of the combining form (contrast, e.g., gas meter n. at gas n.¹ and adj. Compounds 3 with gasometer n.).