In linguistic morphology, fossilization refers to two close notions. One is preserving of ancient linguistic features which have lost their grammatical functions in language. Another is loss of productivity of a grammatical paradigm (e.g. of an affix), which still remains in use in some words.
The term fossilization or interlanguage fossilization is also used in linguistics to refer to the process in which incorrect linguistic features become a permanent part of the way a person speaks and writes a new language, especially when not learned as a young child.
- The Dictionary of Historical and Comparative Linguistics, by Robert Lawrence Trask, p. 125