Non-finite verb forms

the number. Infinitive answers questions: what to do?

a verb, adverb and adjective.
The present participle is formed by the end  -ing:
to learn – learning
The past participle is also an impersonal form of the verb, also having the properties of the verb, adjective and adverb. But unlike the present participle, the past participle has only one unchangeable form, in fact, it is the third form of the ver