How do you spell Fastness

Available Definitions:
1)  a. - The state of being fast and firm; firmness; fixedness; security; faithfulness.
2)  a. - A fast place; a stronghold; a fortress or fort; a secure retreat; a castle; as, the enemy retired to their fastnesses in the mountains.
3)  a. - Conciseness of style.
4)  a. - The state of being fast or swift.