terra

Terra, terrae is first declension feminine, and nearly every noun of that declension is feminine, which makes it a safe model to learn from. Its ablative terra carries a long final vowel the nominative does not, and in speech that length is the only thing separating on land from the land; it is the form in the fixed phrase terra marique. English takes terrain, terrestrial, territory and subterranean from it, and Mediterranean is medius plus terra, in the middle of the land.