In linguistic morphology, fossilization refers to two close notions. One is preserving of ancient linguistic features which have lost their grammatical functions in language

Language

Language may refer either to the specifically human capacity for acquiring and using complex systems of communication, or to a specific instance of such a system of complex communication...

. Another is loss of productivity of a grammatical paradigm (e.g., of an affix

Affix

An affix is a morpheme that is attached to a word stem to form a new word. Affixes may be derivational, like English -ness and pre-, or inflectional, like English plural -s and past tense -ed. They are bound morphemes by definition; prefixes and suffixes may be separable affixes...

), which still remains in use in some words.

Examples of fossilization include fossilized morpheme

Bound morpheme

In morphology, a bound morpheme is a morpheme that only appears as part of a larger word; a free morpheme is one that can stand alone.Affixes are always bound. English language affixes are either prefixes or suffixes. E.g., -ment in "shipment" and pre- in "prefix"...

s and fossil word

Fossil word

A fossil word is an obsolete word which remains in currency because it is contained within an idiom still in use.It can also occur for phrases, such as in point , which is retained in the larger phrases case in point and in point of fact, but is not otherwise used outside of a legal...

s.