Indo-European copula copula (with corresponding voiceless and voiced fricatives) existed side by side in Germanic, and the involvement of a separate root "" is unnecessary. The root "*(s)teh-" 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. On the absence of the initial s- in Celtic, see Indo-European s-mobile. In Latin, "stō, stare" retained the meaning "to stand", until local forms of Vulgar Latin began to use it as a copula in certain circumstances. Today, this survives in that several Romance languages (Galician-Portuguese, Spanish, Catalan) use it
Indo-European s-mobile alternation between and ('they saw the wolves' ) is plausible. The two variants would still be pronounced differently, as the double -ss- is distinct from a single -s- (compare English "the sink" and "this sink"), but the alternation can now be understood as a simple process of gemination (doubling) or degemination. This can be understood in two ways. A number of roots beginning in look as if they had an s-mobile but the evidence is inconclusive, since several languages (Latin, Greek, Albanian) lost initial "s-" before sonorants ("l, m, n") by regular sound change. Examples include: Indo-European s-mobile In Indo-European