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 ablaut Ablaut is the oldest and most extensive single source of vowel gradation in the Indo-European languages and must be distinguished clearly from other forms of gradation, which developed later, such as Germanic umlaut ("man"/"men", "goose"/"geese", "long"/"length") or the results of modern English word-stress patterns ("man"/"woman", "photograph"/"photography"). Confusingly, in some contexts, the terms 'ablaut', 'vowel gradation', 'apophony' and 'vowel alternation' are used synonymously, especially in synchronic comparisons, but historical linguists prefer to keep 'ablaut' for the specific Indo-European phenomenon, which is the meaning intended by the linguists who first coined the word. In Proto-Indo-European, the basic, inherent vowel of most syllables