IPA: /ˈɡeɪ.ʃəs/
KK: /ˈɡeɪʃəs/
Relating to or existing in the form of gas; not solid or liquid.
The gaseous state of water is known as steam.
Gaseous → It is formed from "gas" (from Latin *gas*, meaning a state of matter that is neither solid nor liquid) and the suffix "-eous" (meaning having the nature of). The word "gaseous" describes something that has the nature of gas.
Think of the word 'gas' which refers to a state of matter, and remember that 'gaseous' means having the nature of gas.