Whether word formation and lexicalization refer to the same process is controversial within the field of linguistics.
[1] Lexicalization may be simple, for example borrowing a word from another language, or more involved, as in calque or loan translation, wherein a foreign phrase is translated literally, as in marché aux puces, or in English, flea market.
[2] Particularly interesting from the perspective of historical linguistics is the process by which ad hoc phrases become set in the language, and eventually become new words (see lexicon).
The most widely accepted model, speech production, in which an underlying concept is converted into a word, is at least a two-stage process.
First, the semantic form (which is specified for meaning) is converted into a lemma, which is an abstract form specified for semantic and syntactic information (how a word can be used in a sentence), but not for phonological information (how a word is pronounced).