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 copula is more frequently used than any other, and partly because Proto-Indo-European offered more than one verb suitable for use in these functions, with the result that the daughter languages, in different ways, have tended to form suppletive verb paradigms. This article describes the way in which the irregular forms have developed from a series of roots. The root "*hes-" was certainly already a copula in Proto-Indo-European. The e-grade (see Indo-European ablaut) is found in such forms as English "is", Irish "is", German "ist", Latin "est", Sanskrit "asti", while the zero grade produces forms beginning with /s/, like German "sind", Latin