noun

osmosis

oz-MOH-siss

Osmosis (noun) means the movement of a solvent, usually water, through a semi-permeable membrane from a weaker solution into a stronger one, so that the concentrations tend to even out. Example: “Water enters the root hairs by osmosis because the cell sap is more concentrated than the surrounding soil water.”

noun

The movement of a solvent, usually water, through a semi-permeable membrane from a weaker solution into a stronger one, so that the concentrations tend to even out.

"Water enters the root hairs by osmosis because the cell sap is more concentrated than the surrounding soil water."

"Put the potato slices in salt water and osmosis will draw the moisture out."

figurative The gradual, unconscious absorption of knowledge, habits or attitudes simply by being around them.

"He never studied the rules; he learned them by osmosis from watching his father play."

"Office jargon spreads by osmosis."

How to Use Osmosis

Learner’s notes

In plain EnglishWater moving through a membrane towards the saltier side; or picking something up just by being around it.

When to use it

Technical in biology and chemistry; the figurative sense is informal and very common.

Memory tip

The adjective is osmotic, as in osmotic pressure. The plural is osmoses, but it is rarely needed.

Trace the full origin ↓

Easily confused with

diffusion → active transport dialysis →

Common pairings

by osmosis reverse osmosis osmosis across the membrane learn by osmosis

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Fill the Gap

Can you complete this real example?

Water enters the root hairs by _____ because the cell sap is more concentrated than the surrounding soil water.

Etymology

From Greek osmos 'a pushing, thrusting', with the noun ending -osis; it entered scientific English in the nineteenth century.

Origin: Greek

Rhymes for osmosis

meiosis mitosis stenosis necrosis neurosis hypnosis fibrosis diagnosis prognosis symbiosis halitosis psychosis

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Frequently Asked Questions

What is the difference between osmosis and diffusion?

Diffusion is any movement of particles from where they are concentrated to where they are not. Osmosis is the special case in which it is the solvent, usually water, moving across a semi-permeable membrane, because the dissolved particles themselves cannot pass through.

Which way does water move in osmosis?

From the dilute side to the concentrated side, in other words from high water potential to low water potential. That is why a cell placed in salty water shrinks and one placed in pure water swells.

What is reverse osmosis?

It is osmosis driven backwards by applying pressure to the concentrated side, forcing water through the membrane and leaving the dissolved salts behind. It is the basis of most desalination and many domestic water filters.