Fold up and Fall down

Fold up verb - Bend or lay so that one part covers the other.

Fall down and fold up are semantically related in collapse inward topic. In some cases you can use "Fall down" instead a verb "Fold up".

Fall down verb - Lose an upright position suddenly.

Fold up and fall down are semantically related in collapse inward topic. Sometimes you can use "Fold up" instead a verb "Fall down".