*mē-, Proto-Indo-European root meaning "to measure." Some words may belong instead to root *med- "to take appropriate measures."

It forms all or part of: amenorrhea; centimeter; commensurate; diameter; dimension; gematria; geometry; immense; isometric; meal (n.1) "food, time for eating;" measure; menarche; meniscus; menopause; menses; menstrual; menstruate; mensural; meter (n.1) "poetic measure;" meter (n.2) unit of length; meter (n.3) "device for measuring;" -meter; Metis; metric; metrical; metronome; -metry; Monday; month; moon; parameter; pentameter; perimeter; piecemeal; semester; symmetry; thermometer; trigonometry; trimester.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit mati "measures," matra "measure;" Avestan, Old Persian ma- "to measure;" Greek metron "measure," metra "lot, portion;" Latin metri "to measure."

"to allot," Old English metan (West Saxon mæton), "to measure, ascertain the dimension or quantity of; measure out; compare; estimate the greatness of value of" (class V strong verb; past tense mæt, past participle meten), from Proto-Germanic *metana "to measure" (source also of Old Saxon metan, Old Frisian, Old Norse meta, Dutch meten, Old High German mezzan, German messen, Gothic mitan "to measure"), from PIE root *med- "take appropriate measures." Meaning "distribute or apportion by measure" is from c. 1300 and is the surviving sense, used now exclusively with out. Related: Meted; meting.

chiefly British English spelling of meter (n.); for spelling, see -re.

1670s, from hydro- + meter (n.3). Related: Hydrometric; hydrometry.

instrument for measuring the difference of potentials in volts, 1882, from volt + meter (n.3).

also centimetre, metric measure of length, "one hundredth of a meter," 1801, from French centimètre (18c.), coined from Latin centum "hundred" (see hundred) + French mètre (see meter (n.2)).

"measure of length equal to the tenth part of a meter, 1809, from deci- + meter (n.2).

"one thousand meters," 1810, from French kilomètre (1795); see kilo- + meter (n.2). Related: Kilometric.

1570s, "insert (a name) in a register or official list," especially "to admit (a student) to a college by enrolling his name on the register," from Late Latin matriculatus, past participle of matriculare "to register," from Latin mātricula "public register," diminutive of mātrix (genitive mātricis) "list, roll," also "sources, womb" (see matrix).

The connection of senses in the Latin word seems to be via confusion of Greek mētra "womb" (from mētēr "mother;" see mother (n.1)) and an identical but different Greek word mētra meaning "register, lot" (see meter (n.2)). Evidently Latin mātrix was used to translate both, though it originally shared meaning with only one.

Intransitive sense of "to be entered as a member of a university or college, to become a member of a body or society" is by 1851. Also from late 16c. in English as "to adopt as a child; to naturalize," from the other sense of the Latin word, but these meanings now are obsolete. A list or register of persons belonging to an order, society, etc. was a matricula (1550s), from a diminutive of Latin mātrix. Related: Matriculated; matriculating.

"pertaining to the system of weights and measures based on the meter," 1855, from French métrique, from mèter (see meter (n.2)). In this sense, metrical is attested from 1797. Metric system is attested by 1855.