There are exceptions to the rules of building the plural of Green nouns.

1. Greek isles with a -ος suffix are grammatically female:
   💡 Examples:
   η Κύπρος – Cyprus
   η Σάμος – Samos
   η Νάξος – Naxos
   η Ρόδος – Rhodes
   η Λέσβος – Lesvos
   η Σύρος – Syros
2. Some other nouns with a -ος suffix are feminine as well, however, they are declined like masculine nouns with a -ος suffix:
   💡 Examples:
   Singular
   η είσοδος – the entrance
   η έξοδος – the exit
   Plural
   οι είσοδοι – the entrances
   οι έξοδοι – the exits
3. There are feminine nouns with an -η ending changing their endings into -εις endings in the plural mode:
   💡 Examples:
   Singular
   η λέξη – the word
   η πρόταση – the sentence
   Plural
   οι λέξεις – the words
   οι προτάσεις – the sentences
4. Feminine nouns with an -α suffix change their suffix into -αδες in the plural mode:
   💡 Examples:
   Singular
   η μαμά – the mom
   η γιαγιά – the grandmom
   Plural
   οι μαμάδες – the moms
   οι γιαγιάδες – the grandmoms
5. Masculine nouns with an -ας ending change into an -αδες ending in the plural mode:
   💡 Examples:
   Singular
   ο μπαμπάς – the dad
   ο ψαράς – the fisherman
   Plural
   οι μπαμπάδες – the dads
   οι ψαράδες – the fishermen
   
6. Some feminine nouns with an -ου ending change into an -ουδες ending in the plural mode:
   💡 Examples:
   Singular
   η αλεπού – the fox
   Plural
   οι αλεπούδες – the foxes