hard

adjective:solid, firm, and resistant to pressure
- The wood is hard and durable, making it ideal for furniture.
adjective:difficult to bear, endure or deal with
- She's going through a hard time after her loss.
adjective:requiring great mental effort; difficult to understand or solve
- The final exam was incredibly hard.
adjective:unyielding or inflexible in attitude or character
- She is hard when it comes to negotiating contracts, never giving in easily.
adverb:with a great deal of effort or force
- She worked hard to achieve her goals.