"Solid, liquid, and gas."

[I.Schmidt1]

Solid, liquid, and gas. are these nouns or adjectives or nominalized adjective?
Στερεό,υγρό και αέριο. these are nouns!?
can I also use στερεά, υγρά και αέρια

[troll1995]

Both the English and the Greeks one are nominalized adjectives (so, they are nouns now). You can say στερεά, υγρά και αέρια but this translates as solids, liquids and gases.