To form the present participle, the suffix ing is generally added to the basic form: The infinitive form is a compound verb made up of the preposition to and the basic form: The basic form (or root) is the form listed in the dictionary, which is generally the first-person singular of the simple present tense (except in the case of the verb to be): There are four principal forms: basic or root, present participle, past and past participle.
English verb tenses are formed by combining one of the principal forms of a main verb with one or more auxiliary verbs.
