clin

The root clin comes from Latin clīnāre, meaning "to lean, bend, or slope" — and its Greek cousin klinein, with the same sense of leaning or tilting. The core image is simple and physical: a thing tipped off vertical, leaning in some direction.

Latin built a family by attaching prefixes that tell you which way the leaning goes:

- in- (toward) + clīnāre → incline: lean toward something. Physically a slope; figuratively a tendency — "I'm inclined to agree" means my mind leans that way.
- de- (down, away) + clīnāre → decline: lean down. The downward lean became "decrease" (sales decline) and, by a polite sidestep, "to turn away" an offer — you lean away from it. Hence decline an invitation.
- re- (back) + clīnāre → recline: lean back. The relaxed backward tilt of a chair or a body.
- pro- (forward) + clīvus (slope) → proclivity: a forward lean toward something — a strong natural tendency, often for a vice.
- de- (down) + clīvus → declivity: a downward slope, a hillside falling away.

Notice the variant cliv: Latin had both the verb clīnāre (to lean) and the noun clīvus (a slope, hillside). They are the same idea — a lean made permanent into a hill — so proclivity and declivity are the "slope" branch of the family.

Two members surprise people:

- client comes from Latin cliēns, "one who leans on" — a commoner who depended on a powerful patron for protection in ancient Rome. The patron stood upright; the client leaned on him. That dependence is why your lawyer's clients lean on her services today.
- climate comes through Greek klima, "a slope, a zone" — specifically the way the Earth's surface tilts away from the sun at different latitudes. Ancient geographers divided the world into klimata, bands of inclination toward the sun. The angle of the slope decided the weather, so klima came to mean the weather itself.
- clinical comes from Greek klinē, "a bed" (literally "a thing you lean/lie back on"). A clinic was originally bedside medical teaching, so clinical means "at the patient's bedside" — and, by extension, the cool, detached manner of a doctor examining a patient.

The whole family is one gesture in many directions: lean in (incline), lean down (decline, declivity), lean back (recline), lean forward (proclivity), lean on (client), tilt away from the sun (climate), or lie back on a bed (clinical).