early 15c. (earlier superflue, late 14c.), from Latin superfluus "unnecessary," literally "overflowing, running over," from superfluere "to overflow," from super "over" (see super-) + fluere "to flow" (see fluent). Related: Superfluously; superfluousness.

early 15c., "a flowing together, especially of two or more streams," from Late Latin confluentia, from Latin confluentem (nominative confluens), present participle of confluere "to flow together," from assimilated form of com "with, together" (see con-) + fluere "to flow" (see fluent).

mid-15c., from Old French fluctuacion (12c.) or directly from Latin fluctuationem (nominative fluctuatio) "a wavering, vacillation," noun of action from past-participle stem of fluctuare "to undulate, to move in waves," from fluctus "a wave, billow, surge, a flowing," from past participle of fluere "to flow" (see fluent).

early 15c., "a flowing back" (of the sea, etc.), "ebb tide," also figurative of instability, from Medieval Latin refluxus, from Latin re- "back, again" (see re-) + fluxus "a flowing," from fluere "to flow" (see fluent). Digestive sense is recorded from 1937; reflux-valve is attested by 1853.

"flowing together, meeting in their courses," late 15c., from Latin confluentem (nominative confluens), present participle of confluere "to flow together," from assimilated form of com "with, together" (see con-) + fluere "to flow" (see fluent). The noun meaning "a stream which flows into another" is from 1850.

mid-15c., from Latin effluentem (nominative effluens) "flowing out," present participle of effluere "to flow out," from assimilated form of ex "out" (see ex-) + fluere "to flow" (see fluent). As a noun, "that which flows out," from 1859; specific meaning "liquid industrial waste" is from 1930.

early 15c., "sweet as honey, pleasing, sweetly or smoothly flowing" (of an odor, a style of speaking or writing, etc.), from Late Latin mellifluus "flowing with (or as if with) honey," from Latin mel (genitive mellis) "honey" (related to Greek meli "honey;" from PIE root *melit- "honey") + -fluus "flowing," from fluere "to flow" (see fluent). Related: Melifluously; melifluousness.

late 14c., "abnormally copious flow," from Old French flus "a flowing, a rolling; a bleeding" (Modern French flux), or directly from Latin fluxus (adj.) "flowing, loose, slack," past participle of fluere "to flow" (see fluent). Originally "excessive flow" (of blood or excrement), it also was an early name for "dysentery;" sense of "continuous succession of changes" is first recorded 1620s. The verb is early 15c., from the noun.

1660s, an old chemistry term for "minerals which were readily fusible and useful as fluxes in smelting" [Flood], from Latin fluor, originally meaning "a flowing, flow," from fluere "to flow, stream, run, melt" (see fluent). Said to be from a translation of the German miners' name, flusse. Since 1771 applied to minerals containing fluorine, especially calcium fluoride (fluorspar or fluorite).

early-15c., "abounding in, copious" (of God's grace); mid-15c. "flowing to" (of liquids), both senses now obsolete, from Old French afluent (14c.) or directly from Latin affluentem (nominative affluens) "abounding, rich, copious," literally "flowing toward," present participle of affluere "flow toward," from assimilated form of ad "to" (see ad-) + fluere "to flow" (see fluent). The especial sense of "abounding in wealth or possessions" is from 1753.