The building blocks of English

Affixes

milli-

One thousandth; a thousand.

Latin mille, thousand.

This is one of the standard SI (Système International) decimal prefixes (see the entryNumber words). Examples are milligram, millimetre (US millimeter), and milliwatt. In a very few terms, the sense of the Latin stem is preserved, the only common one being millipede, an invertebrate with (figuratively) a thousand legs. The Latin stem also appears in million (Latin mille plus the augmentative suffix ‑one), and in milliard, an old British term for one thousand million. However, milliner, a person who makes or sells women's hats, derives from the name of the Italian city of Milan.