Morphemes are the indivisible basic units of language, much like the atoms which physicists once assumed were the indivisible units of matter. English speakers borrowed morpheme from French morphème, which was itself created from the Greek root morphē, meaning "form." The French borrowed -ème from their word phonème, which, like English phoneme, means "the smallest unit of speech that can be used to make one word different from another word." The French suffix and its English equivalent -eme are used to create words that refer to distinctive units of language structure. Words formed from -eme include lexeme ("a meaningful linguistic unit that is an item in the vocabulary of a language"), grapheme ("a unit of a writing system"), and toneme ("a unit of intonation in a language in which variations in tone distinguish meaning").