Program or software module which attempts to validate the
spelling of a
word, often by attempting to match it against a simple list of known words, sometimes less naively by detecting constructed words from a list of roots and valid suffices.
Often, modern spellcheckers attempt to provide the correct spelling of an unrecognized word by finding close matches based on one-place character transpositions, low numbers of replaced characters, and sometimes by brain-dead or semi-intelligent phonetic substitutions.
Early spellcheckers created a new genre of computer humor where one would attempt to spell-check proper names of people or places, and attempt to gain cynical insight from the suggested corrections. For example, "HPUX" corrected becomes "hopeless", etc.
The spellchecker is the forerunner of the grammar-checker and successor to the simple hyphenator.
Spellcheckers now exist for a large variety of languages, including non-natural languages like Esperanto and even Klingon, as well as specialized databases for medical and scientific terms.