Plurals of masculine nouns in '-co' and '-go': 'fuochi', 'alberghi' and the exceptions
Many everyday Italian nouns end in -co or -go: fuoco (fire), parco (park), lago (lake), albergo (hotel). To form the masculine plural you replace the final -o with -i. For most of these words, you also add an h: fuochi, parchi, laghi, alberghi. The h keeps the hard k or g sound of the singular.
English speakers often trip over this for two reasons. First, in Italian ci is pronounced like English chee and gi like jee, so writing fuoci or albergi would change the sound of the word. Second, the h is not added every time. Some common words, such as amico, become amici, with a soft sound. This article covers the words that take -chi and -ghi, gives you a rule of thumb for spotting them, and lists the exceptions worth knowing.
gi sounds like jee, ghi sounds like ghee (hard g, as in give)
When a noun keeps its hard sound in the plural, the h has to appear in the spelling: pacco becomes pacchi, and fungo becomes funghi. You say the plural with the same k or g sound as the singular.
The best rule of thumb depends on stress. If the stress falls on the second-to-last syllable, as in FUOco, PARco, LAgo or alBERgo, the plural is usually -chi or -ghi. Almost all two-syllable words follow this pattern, so a short word is a safe bet.
The words
Places and nature
Albergo becomes alberghi, whether it means a hotel or an old-fashioned inn. Parco becomes parchi, lago becomes laghi, and bosco (forest, woods) becomes boschi.
Ci sono molti alberghi in questa strada.
(There are many hotels on this street.)
A Roma ci sono tanti parchi bellissimi.
(In Rome there are lots of beautiful parks.)
In Lombardia ci sono molti laghi.
(There are many lakes in Lombardy.)
Dietro il paese ci sono dei boschi molto grandi.
(Behind the village there are some very large woods.)
Everyday things
Fuoco becomes fuochi, gioco (game) becomes giochi, pacco becomes pacchi, and fungo becomes funghi. You will see funghi on almost every Italian menu.
A Capodanno guardiamo i fuochi d'artificio.
(On New Year's Eve we watch the fireworks.)
I bambini hanno tanti giochi in camera.
(The children have lots of games in their room.)
Oggi sono arrivati due pacchi per te.
(Two parcels arrived for you today.)
Vorrei una pizza con i funghi, per favore.
(I'd like a pizza with mushrooms, please.)
People
Cuoco becomes cuochi. This one is useful because many other words for people do not add the h (see below).
I cuochi preparano la cena.
(The cooks are preparing dinner.)
Watch out
Stress on the third-to-last syllable
When the stress falls earlier in the word, the plural usually turns soft: medico (MEdico) becomes medici, and manico (handle) becomes manici. Words for people ending in -logo work the same way: biologo becomes biologi, and psicologo becomes psicologi.
Common exceptions
A few short words break the rule of thumb and take a soft plural even though the stress falls on the second-to-last syllable. Amico becomes amici, nemico becomes nemici, and greco becomes greci. Learn these individually.
Stasera esco con i miei amici.
(Tonight I'm going out with my friends.)
Feminine words are simpler
Feminine nouns in -ca and -ga always keep the hard sound: amica becomes amiche, and riga becomes righe. The tricky choice between soft and hard only affects masculine nouns.
The typical mistake is to write alberghi without the h, or to pronounce funghi with a j sound. If you are unsure how a written plural sounds, read chi and ghi with a hard k or g.
Summary
Masculine nouns in -co and -go that are stressed on the second-to-last syllable usually add an h in the plural to keep their hard sound: fuochi, parchi, laghi, alberghi, cuochi. Words stressed earlier usually go soft (medici, biologi). Also remember the short exceptions amici and nemici.