cad

The root cad comes from Latin cadere, "to fall." Start with the most physical picture: something drops. A leaf lets go of a branch, a body collapses, a beat lands. From this single image, Latin grew two big branches of meaning.

The first branch stays literal. cadence is the way a rhythm falls into place — the rise and fall of a voice, the closing fall of a piece of music. cadaver is one who has fallen and not gotten up — a corpse. deciduous (de- 'off' + cadere) describes trees whose leaves fall off each autumn. And decadence (de- 'down' + cadere) is a falling down from a high standard — a culture sliding downhill into self-indulgence.

The second branch is where the magic happens. In Latin, when an event "fell out" or "fell upon" someone, it simply happened. We still say things "befall" us and the dice "fall" a certain way. So cadere became the root of happening and chance:

- ad- (toward) + cadere → accident: something that falls toward you unplanned — a mishap.
- in- (in, onto) + cadere → incident: something that falls in — an event, an occurrence.
- co- (together) + in + cadere → coincide: two things fall onto the same point at once.
- ob- (in front of) + cadere → occasion: circumstances fall in front of you — a moment, an opportunity.

English even kept a softened, French-worn version: chance came through Old French cheance from cadere — literally "a falling out," the way things happen to land. Roll the dice and see how they fall: that is chance.

The spelling shifts you'll see are regular: the present stem is cad- (cadence, cadaver), the combining form before a consonant is often cid- (accident, incident, coincide — note the i), and the perfect/supine stem is cas- (case, occasion, casual). They all trace back to the same falling.

One trap worth flagging up front: the -cid- in accident (cadere, fall) looks identical to the -cid- in suicide and decide — but that one is a different Latin verb, caedere "to cut/kill." Falling vs. cutting: same English spelling, unrelated origins. (See related roots.)