mois

Mo is a French noun meaning a month, a unit of time used in many calendars. The term Mois comes from Latin mensis, passed into Old French as mois, and it is cognate with the Spanish mes, Italian mese, and other Romance forms. The noun is masculine; the singular is un mois and the plural is des mois (or les mois) in context, though the written form is the same.

In the Gregorian calendar, which is widely used today, there are twelve months: janvier, février, mars, avril, mai, juin, juillet, août, septembre, octobre, novembre, décembre. Their lengths vary: February has 28 days in common years and 29 in leap years; the other months have 30 or 31 days in a fixed pattern.

Moins can also refer to lunar months in lunar calendars. A synodic month—the average time from new moon to new moon—is about 29.53 days. Lunar calendars commonly use months of 29 or 30 days, totaling about 354 or 355 days per year. Some lunisolar calendars add intercalary or leap months to stay in sync with the solar year.

Usage and origins: In everyday French, mois is used to express duration or time frames, as in pendant un mois or depuis plusieurs mois. The names of the months largely derive from Latin forms (Ianuarius, Februarius, Martius, etc.) adapted through French history, reflecting the Roman calendar and later reforms.