Some past participles are irregular ... The first part of the perfect tense is the present tense of the verb haber, which is known as an auxiliary verb. An auxiliary verb, also called a helping ...

In your scientific paper, use verb tenses (past, present, and future ... such as an infinitive (to do) or a participle (doing), its subject is implied to be the subject of the clause, or sometimes ...

The present participle is a word formed from a verb. The English translation of the present participle ends in -ing. It can be used as a verb or as an adjective.