early 15c., "having an analogous relationship (to), answering, matching," a sense taken up since 19c. by corresponding; from Medieval Latin correspondentem, present participle of correspondere "correspond, harmonize, reciprocate," from assimilated form of com "together, with (each other)" (see com-) + respondere "to answer" (see respond).
late 14c., "appearance, guise; quality or state of being similar; a comparison; person or thing that resembles another," from Old French similitude "similarity, relationship, comparison" (13c.) and directly from Latin similitudinem (nominative similitudo) "likeness, resemblance," from similis "like, resembling, of the same kind" (see similar).
Middle English kitthe "people, race, kinsmen, family," also "homeland, native region; kinship, relationship; knowledge, news; propriety, custom," from Old English cyðð "kinship, relationship; kinsfolk, fellow-countrymen, neighbors; native country, home; knowledge, acquaintance, familiarity," from cuð "known," past participle of cunnan "to know" (see can (v.)), from PIE root *gno- "to know."
The alliterative phrase kith and kin (late 14c.) originally meant "country and kinsfolk" and is almost the word's only survival in Modern English. Some cognates have evolved different senses, such as Dutch kunde "skill, competence," German Kunde "knowledge, news, tidings."
mid-14c., "nobility of birth, gentle birth," from Old French gentilité (14c.), from Latin gentilitatem (nominative gentilitas) "relationship in the same family or clan," from gentilis "of the same family or clan" (see gentle; also compare gentry). From 1640s as "social superiority." Meaning "state of being gentile" is rare.
1540s, "pertaining to marriage, nuptial," also "pertaining to the relationship of husband and wife," from French conjugal (13c.), from Latin coniugalis "relating to marriage," from coniunx (genitive coniugis) "spouse," which is related to coniugare "to join together," from assimilated form of com "with, together" (see con-) + iugare "to join," from iugum "yoke" (from PIE root *yeug- "to join"). Related: Conjugacy; conjugality.
combining form used from 19c. to represent Latin latus "the side, flank of humans or animals, lateral surface," a word of uncertain origin. The Latin word also was used to express intimacy, attachment, or relationship via the notion of "attach to the side, at the side of."
1630s, "action based on natural instincts," from natural (adj.) + -ism. In philosophy, as a view of the world and humanity's relationship to it involving natural forces only (and excluding spiritualism and superstition), from 1750. As a tendency in art and literature, "conformity to nature or reality, but without slavish fidelity to it," from 1850.
1520s, "process of becoming, or state of being, a son," from French filiation, from Medieval Latin filiationem (nominative filiatio), noun of action from past-participle stem of filiare "to have a child," from Latin filius/filia "son/daughter" (see filial). As "relationship of a son or daughter to a parent" (correlative of paternity) from 1794.