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 migrations a sophisticated system of declension and verbs used a similarly sophisticated system of conjugation. Relationships to other language families, including the Uralic languages, have been proposed but remain controversial. There is no written evidence of Proto-Indo-European, so all knowledge of the language is derived by reconstruction from later languages using linguistic techniques such as the comparative method and the method of internal reconstruction. The Indo-Hittite hypothesis postulates a common predecessor for both the Anatolian languages and the other Indo-European languages, called Indi-Hittite or Indo-Anatolian. Although it is obvious that PIE had predecessors, the Indo-Hittite hypothesis is not widely accepted, and