Substate is a noun. A noun is a type of word the meaning of which determines reality.

What is a substate?

: a state (such as a physical or atomic state) that is a variant or division of another more broadly defined state … each quantum state of a given spin angular momentum is split into a number of substates …— Arthur L. Robinson.

What is sub state government?

(ˈsʌbˌsteɪt) n. (Government, Politics & Diplomacy) a subdivision of a state.