In etymology, two or more words in the same language are called doublets or etymological twins or twinlings (or possibly triplets, and so forth) when they have different phonological forms but the same etymological root. Often, but not always, the words entered the language through different routes. Given that the kinship between words that have the same root and the same meaning is fairly obvious, the term is mostly used to characterize pairs of words that have diverged at least somewhat in meaning. For example, English pyre and fire are doublets with merely associated meanings despite both descending ultimately from the same Proto-Indo-European (PIE) word *péh₂ur.