pycn(o)-

Also pykn(o)‑.

Compact; dense.

Greek puknos, thick.

A pycnocline (Greek klinein, to slope) is a layer in a body of water in which water density increases rapidly with depth; a pycnometer (sometimes pyknometer) measures the relative density of liquids; Pycnogonida (Greek gonu, knee) is a class of marine arthropods, the sea spiders; someone who is pyknic is stocky, with a rounded body and head, thickset trunk, and a tendency to fat; pyknosis is the shrinkage of the nuclear material of a cell into a compact mass, a sign of cell degeneration.