The first meaning is the historical trend of every language to conserve intact its lexical structure of word families, in opposition to foreign influence which are considered 'impure'.
The perceived or actual decline identified by the purists may take the form of a change of vocabulary, syncretism of grammatical elements, or loanwords.
Historically, in the first meaning, linguistic purism was institutionalized in Italy through language academies (of which the 1572 Accademia della Crusca set as a model example in Europe), and their decisions often having the force of law.
This view was contested by the Enlightenment, and the terms purismo and purista (first recorded 1758–9 but not used in print until 1838) were introduced to denote linguistic affectation or archaism.
The neopurismo promoted by Bruno Migliorini from the late 1930s sought a compromise between the needs of Italian to evolve and to maintain its structures.