"The gray avenue."
Translation:Η γκρι λεωφόρος.
You are very clever.
At least islands on -ος are always feminine: η Ζάκυνθος, η Λύμνος, η Σκύρος, η Άνδρος, η Σέριφος, η Μήλος, η Ιος, η Πάρος, η Ναξος, η Αμοργός, ... The same goes for geographical places like: η Κνωςςός, η Φαιστός, η Αλικαρ- νασσός, η Κόρινθος, η Κάρυςτος, η Πελοπόννηςος ( η νήσος/island) ...
But mountains and rivers on -ος are masculine: ο Όλυμπος, ο Παρνασσός, ο Ταϋγετος, ο Αχελώος, ο Έβρος
Towns on -ος can have any gender: ο Βολος, η Αιδηψός, ο Αλμυρός, το Άργος, το Άστρος ...
All masculine nouns end in s (in their default form, nominative and singular). Not all words ending in s are masculine. It could be useful to learn the words together with the article for the gender (η λεωφόρος). If you want to use avenue in a sentence, you will use the feminine article and change the noun as any other masculine noun (because of the final s).
Can anyone speak to the usage distinction between δρόμος and λεωφόρος? As an (American) English speaker, I use "street" and "avenue" close to interchangeably (indeed, I'd probably always use "street" over "avenue" unless actually naming the street, e.g., "First Avenue"). Are the two terms more distinct in Greek?