In linguistics, a word of a spoken language can be defined as the smallest sequence of phonemes that can be uttered in isolation with objective or practical meaning. For many languages, words also correspond to sequences of graphemes ("letters") in their standard writing systems that are delimited by spaces wider than the normal inter-letter space, or by other graphical conventions. The concept of "word" is usually distinguished from that of a morpheme, which is the smallest unit of speech which has a meaning, even if it will not stand on its own.