Etymology
Advertisement
flexible (adj.)

early 15c., "capable of being bent; mentally or spiritually pliant," from Old French flexible or directly from Latin flexibilis "that may be bent, pliant, flexible, yielding;" figuratively "tractable, inconstant," from flex-, past participle stem of flectere "to bend," which is of uncertain origin. Flexile (1630s) and flexive (1620s) have become rare. Related: Flexibly. Coles' dictionary (1717) has flexiloquent "speaking words of doubtful or double meaning."

Related entries & more 
Advertisement
flex (v.)
1520s, "to bend," usually of muscles, probably a back-formation from flexible. Related: Flexed; flexing.
Related entries & more 
flexography (n.)
type of rotary printing technique, 1952, from combining form of flexible (in reference to the plate used) + -graphy in the literal sense.
Related entries & more 
flexor (n.)
1610s, of muscles, Modern Latin, agent noun from stem of Latin flectere "to bend" (see flexible). Alternative form flector attested from 1660s (see flexion).
Related entries & more 
flexuous (adj.)
"full of bends or curves, winding, sinuous," c. 1600, from Latin flexuosus, from flexus (n.) "a bending," from flectere "to bend" (see flexible). From 1620s as "undulating."
Related entries & more 
Advertisement
flexibility (n.)
1610s, of physical things, from French flexibilité (in Old French, "weakness, vacillation") or directly from Late Latin flexibilitatem (nominative flexibilitas), from Latin flexibilis "pliant, yielding" (see flexible). Of immaterial things from 1783.
Related entries & more 
flexure (n.)
1590s, "action of flexing or bending," from Latin flextura, from flectere "to bend" (see flexible). From 1620s as "flexed or bent condition; direction in which something is bent." Picked up in mathematics (1670s), geology (1833).
Related entries & more 
inflect (v.)

early 15c., "to bend inward," from Latin inflectere (past participle inflexus) "to bend in, bow, curve," figuratively, "to change, alter, influence," from in- "in" (see in- (1)) + flectere "to bend" (see flexible). Grammatical sense "to vary by change of form" (especially at the end of a word) is from 1660s. Related: Inflected; inflecting.

Related entries & more 
retroflex (adj.)

"bent backward," 1776, in botany, from Modern Latin retroflexus, past participle of retroflectere "to bend back," from retro "back" (see retro-) + flectere "to bend" (see flexible). The verb "to turn or fold back" (1898) is a back-formation from retroflexed (1806), which is from the adjective. Related: Retroflexion.

Related entries & more 
genuflection (n.)

"act of bending the knee," especially in worship, early 15c., genu-fleccion, from Medieval Latin genuflectionem (nominative genuflexio) "bending of the knee," noun of action from past-participle stem of Late Latin genuflectere "genuflect," properly genu flectere "to bend the knee," from Latin genu "knee" (from PIE root *genu- (1) "knee; angle") + flectere "to bend" (see flexible).

Related entries & more