What form is 'numerārī'?

Question

In chapter X of Orberg's Lingua Latina Per Se Illustrata there is this sentence: Piscēs numerārī nōn possunt.

From the context I would translate this as an infinitive. But the infinitive should be numerāre. Perhaps it is a passive infinitive?

Answer 1

You are correct, this is a passive infinitive: "to be counted".

The passive versions of amāre, habēre, currere, and audīre are amārī, habērī, currī, and audīrī.