Fall – phrasal verb
Fall behind – fail to keep level with
After running 3 miles he started to fall behind the rest of the group.
Fall for – to be tricked into believing a lie
I can’t believe she has fallen for this blatant lie.
Fall in with – to agree to something
We all fell in with his proposals.
Fall out with somebody – have an argument and no longer be friends
I fell out with him over his opinions on politics.
Fall through – to fail to happen
Their holiday plans fell through because of money.
Fall back on – to go to someone for help, to have resources when in trouble
I have some money in the bank to fall back on when the times are tough.