'Facile à lire', 'dur à faire': when the thing is the subject
When you say that something is easy, hard, pleasant or boring to do, French lets you start the sentence with the thing itself: ce livre est facile à lire, this book is easy to read. The adjective is followed by à and an infinitive, and the book is really the object of lire, even though it sits in the subject position. Words like facile, difficile, impossible, agréable and simple all work this way.
English does exactly the same thing with easy to read, so the idea is familiar. The trouble is the little word in the middle. English uses to everywhere, while French switches between à and de depending on how the sentence starts. Learners also tend to add an extra pronoun at the end, which French does not want.
The pattern is: thing + être + adjective + à + infinitive. The thing is what you read, open, follow or cook, and nothing comes after the infinitive, because the thing has already been named at the start.
Compare this with the impersonal version, which starts with il est and uses de. Here the thing comes after the infinitive, as its normal object:
Both sentences mean the same thing. A rule of thumb: if the thing comes first, use à. If il comes first and the thing comes last, use de. Because the thing is the subject, the adjective agrees with it: faciles for the instructions, dure for une décision.
The most common group: facile, aisé (a bit more formal), simple, difficile, dur, compliqué and impossible.
Agréable, plaisant, désagréable and déplaisant describe how it feels to hear, watch or read something. Beau and intéressant fit here too, and so does the classic pénible.
Ennuyeux (or ennuyant, common in Canada), long, dangereux, utile and bon follow the same pattern.
The typical mistake is adding a pronoun after the infinitive, as if the verb still needed an object: ce livre est facile à le lire is wrong. The book is already the subject, so just say ce livre est facile à lire.
The second mistake is mixing the two patterns: ce livre est facile de lire is wrong. With the thing first, it is always à.
In everyday speech you will hear c'est in both patterns. C'est facile à faire means that the thing is easy to do, where c' stands for something already mentioned. C'est facile de faire ça puts the object after the verb, so it takes de, just like il est facile de.
Finally, this is not the same as prêt à or décidé à. There the subject is a person who does the action (je suis prêt à partir). Here the subject is the thing the action is done to.
To say something is easy, hard, pleasant or boring to do, put the thing first and use à + infinitive, with nothing after the verb: cette porte est impossible à ouvrir. If you start with il est instead, switch to de and put the thing after the verb: il est impossible d'ouvrir cette porte.







