Citations:invariable

Adjective: "that cannot be inflected"

 * 1867, Norman Pinney and Emile Arnoult, Pinney and Arnoult's French Grammar, page 438:
 * Attendu, ci-inclus, ci-joint, excepté, passé, supposé, compris, franc de port, when they are before a noun, are used as prepositions or adverbial expressions, and are invariable; after the noun they are used as adjectives, and are variable
 * 1902, A Textbook on French, page 25.6:
 * In this expression the adjective franc is invariable before a noun; but it agrees when the noun precedes.
 * 1948, Maria de Lourdes sá Pereira, Brazilian Portuguese: Grammar, page 59
 * These numerals are invariable with the exception of um and dois, which have the feminine forms given above.
 * 2006, Rosalind Fergusson and Martin H. Manser, The Complete Guide to Grammar
 * Singular invariable nouns include mud and impatience, and plural invariable nouns include scissors and trousers. You cannot have *muds, *impatiences, *a scissor, or *a trouser.