Sound laws · Law 4 · Vowels

French fronts long U to [y]

Spanish

u [u] (kept)

French

u [y]

Italian

u [u] (kept)

Portuguese

u [u] (kept)

Romanian

u [u] (kept)

Catalan

u [u] (kept)

What happened

Latin long Ū stayed [u] in every sister but French, which moved it forward in the mouth, keeping the lips rounded: the tongue position of i with the lips of u, which is [y]. It happened in the early Middle Ages; a Gaulish-substrate origin is often proposed but remains disputed. The spelling never changed, so French u looks the same as its sisters' and sounds different.

Examples

Latin	Italian	Spanish	French	Portuguese	Romanian	Catalan	English relative
LŪNAM‘moon’	luna	luna	lune	lua	lună	lluna	lunar
MŪRUM‘wall’	muro	muro	mur	muro	—	mur	mural
PŪRUM‘pure’	puro	puro	pur	puro	—	pur	pure
DŪRUM‘hard’	duro	duro	dur	duro	—	dur
MŪTUM‘mute (fr muet, a diminutive)’	muto	mudo	muet	mudo	mut	mut	mute
MŪLAM‘she-mule’	mula	mula	mule	mula	—	mula	mule
ACŪTUM‘sharp’	acuto	agudo	aigu	agudo	—	agut	acute

Decoder

A u in any sister's word that French shares is French u [y], not ou: luna, lua, lună → lune; muro, mur → mur. Round your lips for u and say i.

Exceptions

Latin short Ŭ is a different story: it merged with long O and gives o in Spanish, Italian, Portuguese and Catalan and ou or eu in French (CŬRTUM → corto, court, corto; GŬLAM → Italian gola, French gueule); Romanian alone kept it as u (GŬLAM → gură). French ou [u] therefore rarely comes from Latin Ū.

Watch it happen: MŪRUM

What happened

Examples

Decoder

Exceptions

In your word bank