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Invariable adjectives: words like 'mozzafiato', 'pari' and 'online' that never change

Most Italian adjectives change their ending to match the noun: un libro nuovo, delle case nuove. A small but useful group never changes at all. The same form works for masculine and feminine, singular and plural: un panorama mozzafiato, delle viste mozzafiato. Examples include the number words pari and dispari, compounds like monouso and antiproiettile, and borrowed English words such as online, single and part-time.

English speakers rarely struggle with agreement itself. The trouble starts once you have trained yourself to make every adjective agree: you start inventing forms like mozzafiati or monousi. With borrowed words, the opposite habit kicks in and you add an English plural -s, as in freelances. Italian does neither.

Word list
bluA1 blue occhi blu rosaA1 pink fiori rosa arancioA2 orange maglie arancio gratisA2 free biglietti gratis onlineA2 online corsi online singleA2 single amiche single violaA2 purple gonne viola insaporeB1 tasteless zucchine insapore offlineB1 offline mappe offline part-timeB1 part-time lavori part-time bioB2 organic prodotti bio dispariB2 odd pagine dispari freelanceB2 self-employed traduttrici freelance mozzafiatoB2 breathtaking viste mozzafiato pariB2 even numeri pari porporaB2 purple tende porpora indoloreC1 painless cure indolore antiproiettileC2 bulletproof vetri antiproiettile monousoC2 disposable piatti monouso
How it works

An invariable adjective has only one form. The noun and its article still show gender and number as usual, but the adjective stays exactly the same. You can tell there is a plural from dei panorami, not from the adjective.

Abbiamo visto dei panorami mozzafiato.
(We saw breathtaking views.)

Rule of thumb: if the adjective ends in something other than the usual -o/-a/-i/-e pattern, is borrowed from English, or is built from a noun (fiato, uso, dolore), assume it does not change.

The words
Borrowed English words

Words taken from English keep one form and never take a plural -s: online, offline, single, part-time and freelance. The shortened form bio (from biologico) behaves the same way.

Seguo due corsi online di inglese.
(I'm taking two online English courses.)
Ho scaricato delle mappe offline per il viaggio.
(I downloaded some offline maps for the trip.)
Le mie amiche sono ancora single.
(My friends are still single.)
Molti studenti cercano lavori part-time.
(Many students look for part-time jobs.)
Lavoro con due traduttrici freelance.
(I work with two freelance translators.)
Al mercato compro solo uova bio.
(At the market I only buy organic eggs.)
Even and odd

Pari and dispari describe numbers, pages, days and so on, and they never change.

I numeri pari sono a sinistra, quelli dispari a destra.
(The even numbers are on the left, the odd ones on the right.)
Compounds built on a noun

These combine a prefix or verb with a noun: mozza + fiato, mono + uso, anti + proiettile, in + dolore, in + sapore. Because the last part is a noun, there is nothing to agree. The same is true of antifurto.

La banca ha i vetri antiproiettile.
(The bank has bulletproof glass.)
Per la festa abbiamo comprato piatti e bicchieri monouso.
(For the party we bought disposable plates and cups.)
Oggi molte cure dal dentista sono quasi indolore.
(Nowadays many dental treatments are almost painless.)
Queste zucchine sono proprio insapore.
(These courgettes are really tasteless.)
Free of charge

Gratis comes from Latin and also never changes.

Per i bambini i biglietti sono gratis.
(Tickets are free for children.)
Watch out

The typical mistake is to force an ending onto the word: not viste mozzafiate, not piatti monousi, not traduttrici freelances. Leave the word alone.

Bio is informal. Its full form biologico is a normal adjective and does agree: prodotti biologici, frutta biologica.

Gratis also works as an adverb, as in entrare gratis (to get in for free). Single is often a noun too: un single, una single, i single. It is still invariable.

Don't confuse these words with ordinary phrases like senza zucchero or a righe. Those don't change either, but that is simply because they are phrases starting with a preposition, not adjectives. Invariable colour words such as rosa and blu have their own article.

Summary

A handful of Italian adjectives have just one form for every gender and number. This includes borrowed English words (online, single, freelance), pari and dispari, compounds ending in a noun (mozzafiato, monouso, insapore) and gratis. Let the article and the noun show the gender and plural, and never add an Italian ending or an English -s to the adjective.