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
Proto-Indo-European mythology is known as the comparative method. Different schools of thought have approached the subject of Proto-Indo-European mythology from different angles. The Meteorological School holds that Proto-Indo-European mythology was largely centered around deified natural phenomena such as the sky, the Sun, the Moon, and the dawn. This meteorological interpretation was popular among early scholars, such as Friedrich Max Müller, who saw all myths as fundamentally solar allegories. This school lost most of its scholarly support in the late nineteenth and early twentieth centuries. The Ritual School, which first became prominent in the late nineteenth century, holds that Proto-Indo-European myths are best