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'Grossir', 'rougir', 'vieillir': one French verb for 'get fat', 'go red', 'grow old'

English usually describes a change with two words: get fat, go red, grow old, turn pale. French often packs the whole idea into a single verb built on the adjective: gros gives grossir, rouge gives rougir, vieux gives vieillir, maigre gives maigrir.

English speakers tend to reach for devenir plus an adjective, translating word for word. The result is understandable, but it sounds clumsy next to the one-word verb a French speaker would naturally use. Learning this small family of verbs makes your French sound much more natural when you talk about bodies, faces, food and the passing of time.

Word list
grandirA2 to grow up j'ai grandi à Paris = I grew up in Paris grandirA2 to grow il a grandi = he has grown (taller) grossirB2 to gain weight il a grossi = he put on weight maigrirB2 to lose weight maigrir de 5 kilos = lose 5 kilos pâlirB2 to pale il a pâli = he went pale pâlirB2 to fade les couleurs ont pâli = the colours have faded refroidirB2 to get cold laisser refroidir = leave to cool rougirB2 to blush elle rougit = she blushes vieillirB2 to get old ils vieillissent = they are getting old
How it works

Take the adjective, add the -ir ending, and you have a verb meaning to become that adjective. These verbs work on their own, with no se and no devenir: il grossit already means he is getting fatter.

They all follow the regular finir pattern, so the -iss- syllable appears in the plural and in some other forms: je grossis, nous grossissons, ils vieillissent. In the passé composé they take avoir: il a grossi, elle a rougi.

Rule of thumb: when English says get, go, turn or grow plus an adjective, check whether one of these verbs exists before you use devenir.

Il a beaucoup grossi pendant les vacances.
(He put on a lot of weight during the holidays.)
The words
Size and weight

Grandir (from grand) means both to grow up, as a person becoming an adult, and simply to grow bigger or taller. Grossir and maigrir are the everyday verbs for gaining and losing weight.

J'ai grandi dans un petit village près de Lyon.
(I grew up in a small village near Lyon.)
Ton fils a tellement grandi depuis l'été dernier !
(Your son has grown so much since last summer!)
Elle a maigri de cinq kilos en deux mois.
(She lost five kilos in two months.)
Colour

Rougir is to blush or go red in the face. Pâlir covers two changes: a person turning pale, and a colour fading. French has more of these colour verbs, such as jaunir (to turn yellow) and noircir (to blacken).

Elle rougit quand on lui parle.
(She blushes when people talk to her.)
Il a pâli en lisant le message.
(He went pale as he read the message.)
Les rideaux ont pâli au soleil.
(The curtains have faded in the sun.)
Age and temperature

Vieillir is to get old or to age. Refroidir comes from froid with the prefix re- and is the normal verb for food or drinks getting cold.

Mes parents vieillissent, alors je vais les voir plus souvent.
(My parents are getting old, so I visit them more often.)
Mange vite, ta soupe refroidit !
(Eat up, your soup is getting cold!)
Watch out
No se

These verbs express the change by themselves. Say il grossit, never il se grossit.

Change, not state

Elle est rouge describes how she looks right now. Elle rougit describes her going red. Use the verb when something is changing.

Not a free rule

You cannot turn any adjective into a verb. There is no heureuxir or tristir: for those you still need devenir. Learn the verbs that exist as vocabulary.

Some can take an object

A few of these verbs also mean to make something X. For example, refroidir can be used with an object, and blanchir is often used to mean to whiten something. A common phrase is laisser refroidir, to leave something to cool.

Laisse refroidir le gâteau avant de le couper.
(Let the cake cool before you cut it.)
Summary

When English says get, go, turn or grow plus an adjective, French often has one -ir verb built on that adjective: grossir, maigrir, grandir, rougir, pâlir, vieillir, refroidir. Conjugate them like finir, use avoir in the passé composé, never add se, and prefer them to devenir plus an adjective whenever they exist.