means The natural sugar found in milk and dairy products, broken down by the enzyme lactase into simpler sugars your body can absorb.

from From Latin 'lac' (genitive 'lactis'), meaning milk — the same root that gives us 'lactic' and 'lactate.' Chemists coined the term in the 19th century by tacking the sugar-suffix '-ose' onto that milky root, a naming habit shared by glucose and fructose. The Latin 'lac' is itself an ancient word, with possible distant cousins in Greek 'gala' (as in 'galaxy,' the Milky Way) — though linguists treat that link cautiously rather than as settled fact.