CAPITAL: an adjective, meaning several things such as: 
“upper case” (as in a capital “C”)
“punishable by death”
“chief in importance”

CAPITAL: a noun, meaning:
“a town or seat that is the seat of state government”
“wealth in the form of money or property”

CAPITOL: a noun, meaning:
“a building in which a state legislative body meets”
“the building in which the United States Congress meets in Washington” (This particular use of the word word is ALWAYS capitalized.)

For example, “My daughter wrote her name on the wall using large CAPITAL letters.”
For example, “The serial killer might face CAPITAL punishment.”
For example, ““He overlooks the CAPITAL importance of criticism in the work of creation itself.” ~ T.S. Eliot
For example, “The CAPITAL of Cameroon is Yaoundé.”
For example, “They want to raise some extra CAPITAL for their start-up, so they are crowdfunding.”
For example, “The House of Delegates meets at the state capitol building.”
For example, “The Capitol is the main building of the United States Congress.”

Memory tricks:
Capitol has an O like dOme
CapitAl has A lot of meanings
Categories: DGG