Historically speaking, like most of Indo-European languages that make use of suppletive roots to denote ‘to be’, Persian integrates Proto-Indo-European (PIE) verbs *h1es- (to be) and *bhuH (to grow> to become> to be). Hence, while Persian infinitive būdan (to be) < PIE "*bhuH" forms the past stem of the verb (e.g. Persian būd- ‘was’) or acts as an auxiliary verb in formation of pluperfect of other verbs, its present tense is solely based on the derivatives of PIE *"h1es-". It is, in fact, from the declension of PIE *"h1es- (to be) that six present stems have been created and assigned to the 1st, 2nd, and 3rd person singular and plural to act as the present-tense conjugation of Persian būdan" (to be), as shown in the following table.