against

preposition: in opposition to; contrary to
- We are voting against the proposed law.
preposition: in or into physical contact with, so as to provide support or impact
- She leaned the ladder against the wall.
preposition: in anticipation of or preparation for (a difficulty or problem)
- We saved money against a future emergency.
preposition: as a protection from or defense from
- The vaccine protects you against the virus.
preposition: with a background of; creating a contrasting effect with
- The red flag stood out against the blue sky.