N. B.--Bal, ball; carnaval, carnival; régal, a treat, take s.

8. Ciel, oeil, aïeul, have two plurals, as:

aïeul, aïeux, ancestor, ancestors.
ciel, cieux, heaven, heavens.
ciel { tester of a bed;
{sky of a picture;
oeil, yeux, eye, eyes.
aïeul, aïeuls, grandfather, grandfathers.
ciels { testers of beds.
{skies of pictures.
oeils-de-boeuf, oval window, oval windows.

§ 6. Plural of Compound Nouns.

1. When two nouns form a compound, both take the plural ending, as:

chef-lieu, chefs-lieux, chief town, chief towns.
chou-fleur, choux-fleurs, cauliflower.

2. When two nouns are connected by a preposition, the first only takes the plural ending, as:

arc-en-ciel, arcs-en-ciel, rainbow, rainbows.
chef-d'oeuvre, chefs-d'oeuvre, masterpiece, masterpieces.

N. B.--Peculiar are tête-à-tête, private interview, and pied-à-terre, temporary stopping-place, which are invariable.

3. A noun and adjective forming a compound take both the plural ending, as: