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 studies "Tocharo-Celtic". Today, "Indo-European", is well established in English and French literature, while remains current in German literature, but alongside a growing number of uses of . Indo-Hittite is sometimes used for the wider family including Anatolian by those who consider that IE and Anatolian are comparable separate branches. The comparative method was formally developed in the 19th century and applied first to Indo-European languages. The existence of the Proto-Indo-Europeans had been inferred by comparative linguistics as early as 1640, while attempts at an Indo-European proto-language reconstruction date back as far as 1713. However, by the 19th century, still no consensus