I'll copy and paste instread: (GK eat your heart out !)
A dependant is person who is dependent on someone else. (For example, a child is dependent on its parents. Therefore, a child is a dependant of its parents.)
All embassy staff and their dependants must be at the airport by 6 o'clock.
(In this example, the word 'dependants' means spouses and children.)
The word "dependent" is an adjective meaning 'contingent on', 'relying on', 'supported by' or 'addicted to'. The word 'dependant' refers to a person and is a noun.
I am dependent on the weather for a safe crossing.
(reliant on the weather)