Etymology
Advertisement
dependency (n.)

1590s, "condition of being logically dependent; relation of a thing or person to that by which it is supported;" 1610s, "that which depends for its existence upon something else;" see dependent + -cy. Originally also dependancy, on the French model, but the Latinate form gradually pushed this into disuse; see -ance and compare dependant (n.). Meaning "territory subordinate to another nation" is recorded from 1680s.

Related entries & more 
Advertisement
ratio (n.)

1630s, in theological writing, "reason, rationale," from Latin ratio "a reckoning, account, a numbering, calculation," hence also "a business affair; course, conduct, procedure," also in a transferred sense, of mental action, "reason, reasoning, judgment, understanding, that faculty of the mind which forms the basis of computation and calculation." This is from rat-, past-participle stem of reri "to reckon, calculate," also "to think, believe" (from PIE root *re- "to think, reason, count").

Latin ratio often was used to represent or translate Greek logos ("computation, account, esteem, reason") in works of philosophy, though the range of senses in the two do not overlap (ratio lacks the key "speech, word, statement" meaning in the Greek word; see Logos).

The mathematical sense of "relation between two similar magnitudes in respect to quantity," measured by the number of times one contains the other, is attested in English from 1650s (it also was a sense in Greek logos). The general or extended sense of "corresponding relationship between things not precisely measurable" is by 1808.

Related entries & more 
dependencies (n.)

"territories subordinate to another nation," 1680s; see dependency.

Related entries & more 
dependancy (n.)

early variant of dependency (q.v.); rare since c. 1800; see -ance.

Related entries & more 
rational (adj.)

late 14c., racional, "pertaining to or springing from reason;" mid-15c., of persons, "endowed with reason, having the power of reasoning," from Old French racionel and directly from Latin rationalis "of or belonging to reason, reasonable," from ratio (genitive rationis) "reckoning, calculation, reason" (see ratio).

In arithmetic, "expressible in finite terms," 1560s. Meaning "conformable to the precepts of practical reason" is from 1630s. Related: Rationally. It is from the same source as ratio and ration; the sense in rational is aligned with that in related reason (n.), which got deformed in French.

Related entries & more 
Advertisement
co-dependent (adj.)

also codependent, by 1905, in various senses, from co- + dependent. Modern psychological sense "dysfunctionally supporting or enabling another in a relationship in addiction or other self-destructive behavior" is attested from c. 1983. Related: Co-dependence, co-dependency.

Related entries & more 
logarithm (n.)

a mathematical function used to shorten calculation, 1610s, logarithmus, coined in Modern Latin by Scottish mathematician John Napier (1550-1617), literally "ratio-number," from Greek logos "proportion, ratio, word" (see Logos) + arithmos "number" (from PIE *erei-dhmo-, suffixed variant form of root *re- "to reason, count"). Napier invented them and published a table in 1614; the kind now chiefly in use were invented by his contemporary Henry Briggs (1561-1630), a professor of geometry at Gresham College, London.

Related entries & more 
natality (n.)

late 15c., "birth" (Caxton), a sense now obsolete, from natal + -ity. Sense of "birth-rate, ratio of the number of births in a given period to the total of the population" is from 1884, from French natalité, used in the same sense.

Related entries & more 
kill (n.1)

early 13c., "a stroke, a blow," from kill (v.). Meaning "the act of killing" is from 1814 in hunting slang; that of "a killed animal" is from 1878. Lawn tennis serve sense is from 1903. The kill "the knockout" is boxing jargon, 1950. Kill ratio is from 1968, American English.

Related entries & more 
geometrical (adj.)

late 14c., from Latin geometricus "of geometry" (from geometria; see geometry) + -al. Since 16c. it has been opposed to arithmetical in ratio, proportion, etc., reflecting the fact that problems of multiplication formerly were dealt with by geometry, not arithmetic. Related: Geometrically.

Related entries & more