IS, verb intransitive iz. [Latin est.] The third person singular of the substantive verb, which is composed of three or four distinct roots, which appear in the words am, be, are, and is is and was coincide with the Latin esse, and Goth.wesan. In the indicative, present tense, it is thus varied; I am, thou art, he, she, or it, is; we, ye or you, they, are. In writing and speaking, the vowel is often dropped; as, he's gone; there's none left.