Metaphor - in Historical Linguistics

In Historical Linguistics

In historical onomasiology or, more generally, in historical linguistics, metaphor is defined as semantic change based on similarity, i.e. a similarity in form or function between the original concept named by a word and the target concept named by this word.

ex. mouse: small, gray rodent → small, gray, mouse-shaped computer device.

Some recent linguistic theories view language as by its nature all metaphorical; or that language in essence is metaphorical.