# lactose

/ˈɫæktoʊs/ (US) · /lˈæktəʊz/ (UK) · CEFR B2 · Noun

Source: https://englishreference.com/word/lactose
Updated: 2026-05-08

## Definition

a type of sugar found in milk and dairy products. Many people find it hard to digest, which can cause stomach problems.

For teachers: a disaccharide sugar present in milk, consisting of glucose and galactose units. It is broken down in the digestive system by the enzyme lactase.

## Examples

- This milk is special because it does not contain any lactose.
- Many adults develop a sensitivity to lactose and choose plant-based alternatives like almond or soy milk.
- The inability to produce sufficient lactase leads to the fermentation of undigested lactose in the colon, resulting in the gastrointestinal symptoms associated with intolerance.

## Usage notes

- Uncountable in its chemical and dietary sense; often appears in the compound 'lactose intolerance'.

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