sentences:  The secondary forms are a plain form used for the infinitive, a gerund-participle and a past participle.The copula verb "to be" is the only verb to retain some of its original conjugation, and takes different inflectional forms depending on the subject.The first-person present-tense form is "am", the third person singular form is "is", and the form "are" is used in the second-person singular and all three plurals.