Spelling is a set of conventions that regulate the way of using graphemes (writing system) to represent a language in its written form. In other words, spelling is the rendering of speech sound (phoneme) into writing (grapheme). Spelling is one of the elements of orthography, and highly standardized spelling is a prescriptive element.

Spellings originated as transcriptions of the sounds of spoken language according to the alphabetic principle. They remain largely reflective of the sounds, although fully phonemic spelling is an ideal that most languages' orthographies only approximate, some more closely than others. This is true for various reasons, including that pronunciation changes over time in all languages, yet spellings as visual norms may resist change. In addition, words from other languages may be adopted without being adapted to the spelling system, and different meanings of a word or homophones may be deliberately spelled in different ways to differentiate them visually.