Etymology
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unit (n.)
1560s, "single number regarded as an undivided whole," alteration of unity on the basis of digit. Popularized in John Dee's English translation of Euclid, to express Greek monas (Dee says unity formerly was used in this sense). Meaning "single thing regarded as a member of a group" is attested from 1640s. Extended sense of "a quantity adopted as a standard of measure" is from 1738. Sense of "group of wards in a hospital" is attested from 1893.
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area (n.)

1530s, "vacant piece of ground," from Latin area "level ground, open space," used of building sites, playgrounds, threshing floors, etc.; which is of uncertain origin. Perhaps an irregular derivation from arere "to become dry" (see arid), on notion of "bare space cleared by burning." The generic sense of "any particular amount of surface (whether open or not) contained within any set of limits" is from 1560s. Area code in the North American telephone systems is attested from 1959.

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force (v.)
c. 1300, forcen, also forsen, "exert force upon (an adversary)," from Old French forcer "conquer by violence," from force "strength, power, compulsion" (see force (n.)). From early 14c. as "to violate (a woman), to rape." From c. 1400 as "compel by force, constrain (someone to do something)." Meaning "bring about by unusual effort" is from 1550s. Card-playing sense is from 1746 (whist). Related: Forced; forcing.
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*per- (4)

Proto-Indo-European root meaning "to strike," an extended sense from root *per- (1) "forward, through."

It forms all or part of: compress; depress; espresso; express; impress (v.1) "have a strong effect on the mind or heart;" imprimatur; imprint; oppress; oppression; pregnant (adj.2) "convincing, weighty, pithy;" press (v.1) "push against;" pressure; print; repress; reprimand; suppress.

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force (n.)
c. 1300, "physical strength," from Old French force "force, strength; courage, fortitude; violence, power, compulsion" (12c.), from Vulgar Latin *fortia (source also of Old Spanish forzo, Spanish fuerza, Italian forza), noun use of neuter plural of Latin fortis "strong, mighty; firm, steadfast; brave, bold" (see fort).

Meanings "power to convince the mind" and "power exerted against will or consent" are from mid-14c. Meaning "body of armed men, a military organization" first recorded late 14c. (also in Old French). Physics sense is from 1660s; force field attested by 1920. Related: Forces.
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*per- (1)

Proto-Indo-European root forming prepositions, etc., meaning "forward," and, by extension, "in front of, before, first, chief, toward, near, against," etc.

It forms all or part of: afford; approach; appropriate; approve; approximate; barbican; before; deprive; expropriate; far; first; for; for-; fore; fore-; forefather; foremost; former (adj.); forth; frame; frau; fret; Freya; fro; froward; from; furnish; furniture; further; galore; hysteron-proteron; impervious; improbity; impromptu; improve; palfrey; par (prep.); para- (1) "alongside, beyond; altered; contrary; irregular, abnormal;" paradise; pardon; paramount; paramour; parvenu; pellucid; per; per-; percent; percussion; perennial; perestroika; perfect; perfidy; perform; perfume; perfunctory; perhaps; peri-; perish; perjury; permanent; permeate; permit; pernicious; perpendicular; perpetual; perplex; persecute; persevere; perspective; perspire; persuasion; pertain; peruse; pervade; pervert; pierce; portray; postprandial; prae-; Prakrit; pre-; premier; presbyter; Presbyterian; preterite; pride; priest; primal; primary; primate; primavera; prime; primeval; primitive; primo; primogenitor; primogeniture; primordial; primus; prince; principal; principle; prior; pristine; private; privilege; privy; pro (n.2) "a consideration or argument in favor;" pro-; probably; probe; probity; problem; proceed; proclaim; prodigal; produce; profane; profess; profile; profit; profound; profuse; project; promise; prompt; prone; proof; proper; property; propinquity; prophet; prose; prostate; prosthesis; protagonist; Protean; protect; protein; Proterozoic; protest; proto-; protocol; proton; protoplasm; Protozoa; proud; prove; proverb; provide; provoke; prow; prowess; proximate; Purana; purchase; purdah; reciprocal; rapprochement; reproach; reprove; veneer.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit pari "around, about, through," parah "farther, remote, ulterior," pura "formerly, before," pra- "before, forward, forth;" Avestan pairi- "around," paro "before;" Hittite para "outside of," Greek peri "around, about, near, beyond," pera "across, beyond," paros "before," para "from beside, beyond," pro "before;" Latin pro "before, for, on behalf of, instead of," porro "forward," prae "before," per "through;" Old Church Slavonic pra-dedu "great-grandfather;" Russian pere- "through;" Lithuanian per "through;" Old Irish ire "farther," roar "enough;" Gothic faura "before," Old English fore (prep.) "before, in front of," (adv.) "before, previously," fram "forward, from," feor "to a great distance, long ago;" German vor "before, in front of;" Old Irish air- Gothic fair-, German ver-, Old English fer-, intensive prefixes.

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*per- (3)

Proto-Indo-European root meaning "to try, risk," an extended sense from root *per- (1) "forward," via the notion of "to lead across, press forward."

It forms all or part of: empiric; empirical; experience; experiment; expert; fear; parlous; peril; perilous; pirate.

It is the hypothetical source of/evidence for its existence is provided by: Latin experiri "to try," periculum "trial, risk, danger;" Greek peira "trial, attempt, experience," empeiros "experienced;" Old Irish aire "vigilance;" Old English fær "calamity, sudden danger, peril, sudden attack," German Gefahr "danger," Gothic ferja "watcher.

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*per- (5)

Proto-Indo-European root meaning "to traffic in, to sell," an extended sense from root *per- (1) "forward, through" via the notion of "to hand over" or "distribute."

It forms all or part of: appraise; appreciate; depreciate; interpret; praise; precious; price; pornography.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit aprata "without recompense, gratuitously;" Greek porne "prostitute," originally "bought, purchased," pernanai "to sell;" Latin pretium "reward, prize, value, worth;" Lithuanian perku "I buy."

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per- 

word-forming element common in words of French and Latin origin, meaning primarily "through," thus also "throughout; thoroughly; entirely, utterly," from Latin preposition per (see per (prep.)).

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*per- (2)

Proto-Indo-European root meaning "to lead, pass over." A verbal root associated with *per- (1), which forms prepositions and preverbs with the basic meaning "forward, through; in front of, before," etc.

It forms all or part of: aporia; asportation; comport; deport; disport; emporium; Euphrates; export; fare; farewell; fartlek; Ferdinand; fere; fern; ferry; firth; fjord; ford; Fuhrer; gaberdine; import; important; importune; opportune; opportunity; passport; porch; pore (n.) "minute opening;" port (n.1) "harbor;" port (n.2) "gateway, entrance;" port (n.3) "bearing, mien;" port (v.) "to carry;" portable; portage; portal; portcullis; porter (n.1) "person who carries;" porter (n.2) "doorkeeper, janitor;" portfolio; portico; portiere; purport; practical; rapport; report; sport; support; transport; warfare; wayfarer; welfare.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit parayati "carries over;" Greek poros "journey, passage, way," peirein "to pierce, pass through, run through;" Latin portare "to carry," porta "gate, door," portus "port, harbor," originally "entrance, passage," peritus "experienced;" Avestan peretush "passage, ford, bridge;" Armenian hordan "go forward;" Old Welsh rit, Welsh rhyd "ford;" Old Church Slavonic pariti "to fly;" Old English faran "to go, journey," Old Norse fjörðr "inlet, estuary."

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