Lactose

How to spell lactose

7 letters · 2 syllables

How to pronounce lactose

Say the part in capitals loudest.

What does lactose mean?

1. nounThe natural sugar present in milk and dairy products, which some adults cannot fully digest.

Lactose in a sentence

• The carton is labelled free of lactose for people who cannot digest dairy.

• His doctor explained that lactose is broken down by an enzyme called lactase.

Where does lactose come from?

Language of origin: Latin

Lactose is a scientific coinage built from the Latin word lac, with the stem lactis, meaning simply 'milk'. To this milk root chemists added the suffix -ose, which had become the standard ending for naming sugars after it was extracted from the French word glucose; you see the same -ose in fructose, sucrose, and maltose. The term was assembled in the nineteenth century to label the particular sugar found in milk, and it entered English in the 1840s as the chemistry of foods was being worked out. The same lac root survives in everyday relatives such as 'lactic' acid and 'lactate', and even in 'lettuce', which was named for its milky sap. Remembering that the first half means milk and the -ose marks a sugar helps keep the spelling steady: it is lact plus ose, not 'lactos' or 'laktose'.

How the word is built

• lact- (from Latin lac, lactis: milk)
• -ose (chemistry suffix marking a sugar)