“Amici” not “amichi”: why the h comes and goes in Italian plurals.

Amichi and fuoci are both reasonable guesses, and both are wrong, though only one of them is wrong for a reason you can learn. You have met amici and you have met fuochi, you can see that one keeps the hard sound and the other does not, and nothing in either word tells you which is which. So you guess, and half the time the guess is wrong.

Here is the part that most explanations leave out, and it is the reason this question keeps being asked: there is a rule, the rule is dependable, and amico breaks it. Both halves are true at once. If you have been trying to find a pattern that also produces amici, you have been looking for something that is not there.

The rule is about stress. For nouns and adjectives ending in -co and -go, listen to where the beat falls in the singular. If it falls on the syllable immediately before the ending (FUO-co, al-BER-go, LA-go, BIAN-co), the plural keeps the hard sound, and Italian writes that with an h: fuochi, alberghi, laghi, bianchi. If the beat falls earlier than that (ME-di-co, psi-CO-lo-go, sim-PA-ti-co), there is no h: medici, psicologi, simpatici.

The h is not decoration. In Italian spelling, c before i is the sound in “cheese” and ch before i is the sound in “key”, so the h is the only thing keeping -chi hard. Where the hard sound survives into the plural, the h has to be written. Where it softens, the h would be wrong.

Those two last figures are the same word, one sentence apart, spelled two different ways. A group of male or mixed friends is amici; a group of women is amiche. Nothing has gone wrong there: the feminine plural is regular and the masculine plural is the exception, and they happen to belong to the same noun, which is why this particular word is the one everybody trips on.

The edge that trips people up

Four masculine words have the beat in the right place and drop the h anyway. Amico → amici. Nemico → nemici. Greco → greci. Porco → porci. That is the list, and it is worth learning as a list rather than as a pattern, because there is no pattern in it: amico and nemico are a pair by meaning, and the other two are simply along for the ride. Their feminines are all regular: amiche, nemiche, greche.

Counting them out is the useful move here. Four words against every other noun in -co, which is a proportion you can live with. You are not choosing between two systems; you are applying one rule and keeping four words in your pocket.

The mirror image is easier and deserves saying plainly. Feminine nouns and adjectives in -ca and -ga always take -che and -ghe. Amica → amiche. Collega → colleghe. Banca → banche. Barca → barche. Antica → antiche. The stress makes no difference, and there are no exceptions worth knowing at this level. When the word is feminine, you can stop thinking.

One more complication belongs here, because you will meet it and it looks like a broken rule. The stress test is dependable for -co. For -go the h is stickier: several words with the beat further back still keep it, as in dialogo → dialoghi and catalogo → cataloghi. The most useful group that does drop it is the one in -logo naming a person (psicologo → psicologi, biologo → biologi, archeologo → archeologi), though it is not the only group that does. So if the word ends in -go and does not describe somebody’s profession, expect the h.

The rule applies to adjectives exactly as it does to nouns, and adjectives are where the plural shows up most often. Un vino bianco, dei vini bianchi. Un film magnifico, dei film magnifici. Un ragazzo simpatico, dei ragazzi simpatici. Bianco has the beat before the ending and keeps the h; magnifico and simpatico have it earlier and do not. The same test, applied to the same syllable.

How to hear it

Say the singular and find the beat. If the beat lands on the syllable right before the ending, expect an h in the plural, unless the word is one of the four. If the beat lands earlier, no h, except in the -go words above, where the h stays unless the word names a profession. For a feminine word, skip the test: always -che and -ghe.

You can run that test with your mouth rather than your memory. You already know how to say fuoco and medico; you are not retrieving a fact about them, you are listening to something you would have said anyway. That is why this rule survives a real conversation while a list of plurals does not.

So the honest total is a rule and four words, and four words is the whole price of admission. Amici, nemici, greci, porci. Everything else in -co answers to where you put the beat, and you already put it in the right place every time you say the singular.