# diffusion

/dɪfˈjuʒən/ (US) · /dɪfjˈuːʒən/ (UK)

Source: https://englishreference.com/word/diffusion
Updated: 2026-08-08

## Senses

### 1. movement of particles

noun · CEFR C1 · Technical

the way gas or liquid molecules spread out and mix together naturally.

For teachers: the net movement of molecules or atoms from a region of high concentration to a region of low concentration as a result of random thermal motion.

- The diffusion of the perfume meant that soon the whole room smelled like roses.
- In biological systems, the diffusion of oxygen across cell membranes is a fundamental process for maintaining cellular respiration.

Usage: Often used with the preposition 'of'.

### 2. spreading of ideas or culture

noun · CEFR C1 · Academic

the way that new ideas, languages, or customs spread from one group of people to another.

For teachers: the process by which cultural traits, social institutions, or linguistic practices spread from one society or community to another.

- The diffusion of Greek culture across the ancient world changed how people lived.
- Sociologists study the diffusion of innovations to understand how new technologies are adopted by different segments of the population.

Usage: Commonly appears in the phrase 'cultural diffusion'.

### 3. scattering of light

noun · CEFR C1 · Technical

the way light spreads out when it hits a rough surface or passes through something like a cloud.

For teachers: the scattering of light by reflection from a rough surface or by transmission through a translucent medium.

- The diffusion of sunlight through the thick curtains made the room feel soft and warm.
- Photographers often use a screen to encourage the diffusion of light, which helps to eliminate harsh shadows on the subject's face.

## Examples

- The diffusion of heat warms the whole room.
- The diffusion of the scent filled the kitchen within minutes.
- In biology, the diffusion of oxygen across cell membranes allows tissues to receive the energy they need to survive.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.