break down

[break down] {v.} (stress on "down") 1. To smash or hit (something) so that it falls; cause to fall by force.

The firemen broke down the door.

2. To reduce or destroy the strength or effect of; weaken; win over.

By helpful kindness the teacher broke down the new boy's shyness.

Advertising breaks down a lot of stubbornness against change.

3. To separate into elements or parts; decay.

Water is readily broken down into hydrogen and oxygen.

After many years, rocks break down into dirt.

4. To become unusable because of breakage or other failure; lose power to work or go.

The car broke down after half an hour's driving.

His health broke down.

When the coach was sick in bed, the training rules of the team broke down.

Compare: GO BACK ON (2).