Something that slopes — that is, something that deviates from the straight horizontal or vertical — can be called an incline. If you like to walk up and down hills, you enjoy walking on inclines.
The Latin root of the word incline is inclinare, meaning "to lean." As a verb, the word incline can mean to bend, so you incline your head. It can also mean to be favorably disposed toward something and you can think of it as having a bent for or leaning toward something. If the weather is nasty, you may be inclined to stay home to watch a movie with a bowl of popcorn at your side.