programming-basics: what is difference among size,length and capacity in programming?

when something can be determined by telling distance from start to end point of something as in array, use the word called "length".

the word "size" is used where you look at measure of the number of element in something which is may or may not in location of successive memory. and you can not find out how many there by measuring distance.

The term "capacity" is used where you are told how much something can hold and at the moment how much it´s holding.