Furthermore, as endings added to the stem of the verbs, these declensional forms have been grammaticalized to shape a general paradigm for the grammatical conjugation of all other verbs; these endings were once auxiliary verbs which evolved into an enclitic. This generalized conjugational paradigm is also applied to the past tense of the verb "būdan" (shown in the table below). However, what is linguistically notable, is the emergence of an "existential be" out of the "copula", viz hast (exists) out of ast (is). The evolution of this exceptional form, might go back to ancient Iranian languages, where ast could have two variants (cf. Avestan which has both as- and has- <PIE *h1es- ‘be’). In the next phase, what we may call a "pseudo-verb appeared, vis. the verb hastan" (to exist) has been "analogically" evolved from hast (exists) and has been conjugated like any other Persian verb (e.g. "hast-am" = literally: *‘"(I) am existence"’→ ‘I exist’).