Welsh (along with the other b- initial forms); Persian imperative bov, past bud and future bâš; and the Slavic infinitive and past, etc. for example Russian (byt’), (byl). PIE became Latin /f/, hence the Latin future participle futūrus and perfect fuī; Latin fīō 'I become' is also from this root, as is the Greek verb (phúō), from which physics and physical are derived. was a preterito-present verb, i.e. Imperfect endings for Present, and can be reconstructed as follows: *h2wes- The root *h2wes- may originally have meant "to live", and has been productive in all Germanic languages. The e-grade is present in the German participle gewesen, the o-grade (*wos-) survives in English and Old High German was, while the lengthened e-grade (*wēs-) gives us English were. (The Germanic forms with /r/ instead of /s/ result from grammatischer Wechsel.) See Germanic strong verb: Class 5. *h1er- This has been claimed as the origin of the Old Norse and later Scandinavian languages' present stem: Old Norse em, ert, er, erum, eruð, eru; the second person forms of which were borrowed into English as art and are. It has also been seen as the origin of the Latin imperfect (eram, eras, erat) and future tenses (ero, eris, erit). However, other authorities link these forms with *h1es- and assume grammatischer Wechsel (/s/→/r/), although this is not normally found in the present stem. Donald Ringe argues that the copula was sometimes unaccented in Pre-Proto-Germanic, which would have then triggered the voicing under Verner's law. He explains the Germanic first person singular form as such, deriving it from earlier , since -zm-, but not -sm-, was assimilated to -mm- in Germanic (for which other evidence exists as well). Furthermore, the third person plural form (from PIE ) shows that this word, too, was unaccented. If the accent had been preserved, it would have become , but that form is not found in any Germanic language. In this view, it is likely that stressed and unstressed varieties of the copula (with corresponding voiceless and voiced fricatives) existed side by side in Germanic, and the involvement of a separate root is unnecessary. The Latin forms could be explained by rhotacism. *steh2- The root *(s)teh2- meant "to stand". From this root comes the present stem of the so-called "substantive verb" in Irish and Scottish Gaelic, tá and tha respectively, as well as taw in Welsh. On the absence of the