Adjectives followed by an infinitive (à, de)

Adjectives followed by "de"

In French, many adjectives must be linked to an infinitive (an unconjugated verb) using a preposition. Use de when the adjective describes a person's feelings or state of mind.

The instructor is thrilled to surf with us.
Le moniteur est ravi de surfer avec nous.

You also use de for impersonal expressions that start with Il est (It is...).

It is impossible to surf this gigantic wave!
Il est impossible de surfer cette vague gigantesque !

Adjectives followed by "à"

On the other hand, use à when the adjective expresses readiness, willingness, or determination to take action.

Are you ready to surf?
Es-tu prêt à surfer ?
I am determined to keep my balance.
Je suis décidé à garder l'équilibre.

You also use à when the subject of the sentence is the actual target of the action—for example, when saying a sensation is "thrilling to discover" or courage is "hard to find".

The sensations of surfing are thrilling to discover.
Les sensations du surf sont passionnantes à découvrir.
The courage you need to surf is hard to find.
Le courage dont tu as besoin pour surfer est difficile à trouver.

Putting it all together

To choose the right preposition, look at what the adjective is doing: use de for feelings and impersonal facts, and à for readiness or describing a subject's traits.

I am willing to try. It is exciting to surf, but impossible to do without courage.
Je suis disposé à essayer. C'est excitant de surfer, mais impossible à faire sans courage.