Nouns that are used only in the singular or only in the plural are called defective and they are.
- Almost all abstract nouns: Il coraggio (courage) – La superbia (pride) – La pietà (mercy) etc.
- Some collective nouns: La gente (people) – La roba (stuff) – Il fogliame (foliage) etc.
- Some disease names: Il raffreddore (colds) – La rosolia (rubella) – Il morbillo (measles) – La malaria (malaria) etc.
- The names of chemical elements and metals: L’ossigeno (oxygen) – L’idrogeno (hydrogen) – Il titanio (titanium) – L’oro (gold) etc.
- Many holiday names: Il Natale (Christmas) – Il Pasqua (Easter) – L’Epifania (Epiphany) – Il Ramadan (Ramadan) etc.
- Names of the months: gennaio (January) – febbraio (February) – marzo (March) etc.
- Names that indicate unique things in nature: L’equatore (equator) – Il Nord (North) – L’Est (East) etc.
- The names of food products: Il grano (grano) – Il mais (corn) – Il farro (farro) – La crusca (bran) – Il pepe (pepper).
Defective nouns that are usually used only in the plural are:
- The nouns that indicate objects made up of two equal parts: Gli occhiali (glasses) – Le forbici (scissors) – Le pinze (pliers) – Le manette (handcuffs) – I calzoni (trousers) – I pantaloni (pants) –Le fauci (jaws) .
- Names indicating a group of objects or actions: Le stoviglie (crockery) – I viveri (food) – I dintorni (surroundings) – Gli annali (annals) – le narici (nostrils).
- Some names of Latin origin: Le ferie (holidays) – Le nozze (weddings) – Le esequie (funerals) – Le tenebre (darkness) – I posteri (posterity).
Defective nouns that are usually used only in the singular are:
Masculine: Il riso (rice) – Il latte (milk) – Il pepe (pepper) etc.
Feminine: La fame (hunger) – La sete (thirst) – La senape (mustard) – La prole (offspring).