Premier and premiere are reserved for the absolute first. Inside compound ordinals (21st, 31st, 41st, 51st, 61st, 81st, 101st) French switches to unieme. The rule is strict and gender-invariable on unieme.
Updated May 2026
French
English
Form
Note
Audio
le premier livre
the first book
premier
Absolute first. Masculine. Abbreviated 1er.
la premiere page
the first page
premiere
Absolute first. Feminine. Abbreviated 1re.
le vingt et unieme siecle
the 21st century
unieme
Compound ordinal. Premier never appears inside a compound.
la trente et unieme edition
the 31st edition
unieme
Same; unieme even for feminine, the form is gender invariable.
le quarante et unieme arrondissement
the 41st arrondissement
unieme
Hypothetical Paris example; rule is the same as 21st and 31st.
When do you use premier and when do you use unieme?
Premier (masculine) and premiere (feminine) are reserved for the absolute first: the first book, the first time, the first floor. Unieme appears only inside compound ordinals: 21st, 31st, 41st, 51st, 61st, 81st, 101st. Premier never enters a compound. The Academie francaise codifies this strictly: vingt et unieme, never vingt et premier.
Is unieme masculine or feminine?
Invariable. Unieme works for both genders. Vingt et unieme livre (masculine), vingt et unieme page (feminine). Only premier inflects (premier / premiere). This is one of the few French ordinals where gender does not show.
How do you say 21st century in French?
Le vingt et unieme siecle. With hyphens after the 1990 rectifications: le vingt-et-unieme siecle. Both spellings are accepted. The abbreviated form is XXIe siecle (Roman numeral + e).
Why is it not vingt et premier?
Historical convention. French treats ordinals built on the unit one as taking -unieme rather than dropping in premier. The same applies in other Romance languages: Italian ventunesimo, Spanish vigesimo primero. The Academie francaise dictionary lists only vingt et unieme.