late 15c., "to make conditions, stipulate," from condition (n.). Meaning "subject to something as a condition" is from 1520s; sense of "form a prerequisite of" is from 1868. Meaning "to bring to a desired condition" is from 1844; psychological sense of "teach or accustom (a person or animal) to certain habits or responses" is from 1909. Related: Conditioned; conditioning.
mid-14c., condicioun, "particular mode of being of a person or thing," also "a requisite or prerequisite, a stipulation," from Old French condicion "stipulation; state; behavior; social status" (12c., Modern French condition), from Medieval Latin conditionem (nominative conditio), properly condicio "agreement; stipulation; the external position, situation, rank, place, circumstances" of persons, "situation, condition, nature, manner" of things, from condicere "to speak with, talk together, agree upon," in Late Latin "consent, assent," from assimilated form of com "together" (see con-) + dicere "to speak" (from PIE root *deik- "to show," also "pronounce solemnly").
Classical Latin condicio was confused in Late Latin with conditio "a making," from conditus, past participle of condere "to put together." The sense evolution in Latin apparently was from "stipulation" to "situation, mode of being."
Meaning "rank or state with respect to ordered society" is from late 14c. in English. From the notion of "prerequisite" comes the sense of "a restricting or limiting circumstance" (late 14c.). Also in Middle English "personal character, disposition" (mid-14c.).
"have fellow-feeling," c. 1600, from French sympathiser, from sympathie (see sympathy). Earlier in a physiological sense (1590s). As "express sympathy," from 1748. Related: Sympathized; sympathizing.
chemical formed in the pineal gland of mammals that regulates certain physiological activities, 1958, from Greek melas "black, dark" (see melano-) + ending from serotonin. So called because its secretion is inhibited by sunlight, or because it changes the skin color of certain reptiles and amphibians.
1570s, in a physiological sense relating to tissue development, from Late Latin elaborationem (nominative elaboratio), noun of action from past-participle stem of Latin elaborare "work out, produce by labor, endeavor, struggle," from ex "out" (see ex-) + laborare "to labor" (see labor (v.)). Meaning "act of working out in great exactness and detail" is from 1610s.