Osmosis
Etymology
From Greek ōsmos, "a push, a thrusting," from ōthein, "to push." The physiologist Henri Dutrochet studied the effect in the 1820s, and the term "osmose," later "osmosis," was coined to name this pushing of fluid across a membrane. The casual sense of learning "by osmosis" borrows the image of passive, gradual seeping-in.
noun · /oz-MOH-sis/
The movement of a solvent, such as water, across a selective barrier from where a solution is dilute toward where it is more concentrated.
What it names
The everyday sense of absorbing something gradually and effortlessly, just by being immersed in it — soaking up a place, a language, or a mood.
Example
She never studied the local slang; she picked it up by osmosis after a year of sharing a flat with three natives.
Related idea
Osmosis is the flow of a solvent across a selective barrier; diffusion is the broader spreading of any substance from crowded regions toward emptier ones.
noun · /oz-MOH-sis/
The gradual, effortless absorption of ideas, knowledge, or habits without deliberate study.
What it names
unconscious learning — picking things up merely by being around them
Example
Living in Rome, she learned Italian almost by osmosis.
Related idea
The science becomes metaphor: knowledge seems to seep from a rich environment into an empty mind as water crosses a membrane — a passive cousin of learning by diffusion.