Rules to make a singular noun plural

To make a singular noun ending in “o” plural, change the “o” to “i”. Here is an example; Naso (nose) to Nasi (noses)

Special note: when the “o” is preceded by an “i” you just drop the “o” and do not add a second “i”. Here is an example; Negozio (store) Negozi (stores)

To make a singular noun ending in “a” plural, change the “a” to “e”. Here is an example; Casa (house) to Case (houses)

Special note: when the “a” is preceded by an “c” or “g” you must add an “h” before the “e” in order to maintain the hard “c” or “g” sound. Here is an example; Amica (friend) Amiche (friends)

To make a singular noun ending in “e” plural, change the “e” to “i”. Here is an example;
Dottore (doctor) to Dottori (doctors)

Nouns ending with an accented vowel or a consonant are invariable and do not change. The article changes. Example;  il sport (the sport) i sport (the sports) & la città (the city) le città (the cities)