Soft is used to describe something that's soft.
- That ball is soft, I think we need to get some air into the ball.
Hard is used to describe something that's hard.
- The ball is now hard.
Or, to express strictness, eagerness, or difficulty.
- He's hard on his little girl.
- I work very hard.
- That game is so hard to complete.
Softly is used when something is handled softly or something like that.
- He closed the door softly.
- I've hardly managed to complete the game.
- I hardly work. (It's complete opposite of "I work very hard"!)
- You're hardly hitting me.
What makes me confusing is, any other word like harden, harder, hardest, can mean to express something's hardness, or make something harder. Still, we can't use hardly in a sentence like this:
- He shut the door hard.
Why can't we just use hardly instead of hard? I do actually feel weird that if we use hardly in that sentence, but why? What is the origin of this?
In my native language, as far as I know we don't have "softly" equivalent word to close a door, but in English, we do. So why not close it "hardly"?