To say that something "looks" or "seems" a certain way, French uses the expression avoir l'air (literally: to have the air).
Agreeing with the Subject
Since the noun air is masculine singular, you might guess that the adjective following it stays masculine singular. However, when describing things (like cars at a dealership), the adjective describes the object itself. Therefore, the adjective agrees with the subject of the sentence in gender and number.
Watch how the adjective cabossé (dented) adds an -e to match the feminine singular subject cette berline (this sedan):
| This sedan looks dented, but it works well. | Cette berline a l'air cabossée, mais elle fonctionne bien. |
The same rule applies in the plural. Here, rouillé (rusty) adds an -s to match the masculine plural subject ces utilitaires (these vans):
| Indeed, these vans look rusty. | En effet, ces utilitaires ont l'air rouillés. |
Finding the Core Subject
Be careful when a subject contains multiple nouns. The adjective must agree with the core noun that is actually being described. Below, rouillée agrees with la suspension (feminine), not the van itself:
| The suspension of this van looks rusty. | La suspension de cet utilitaire a l'air rouillée. |
Here are a few more examples of adjective agreement in action with plural subjects:
| Moreover, the cars that we saw look well maintained. | D'ailleurs, les voitures que nous avons vues ont l'air bien entretenues. |
| These ones look very maneuverable in the city. | Celles-ci ont l'air très maniables en ville. |