What is the difference between length, count and size?
Differences with respect to array and ruby.
length returns the length of an array only, it dosen’t accept any additional arguments. size is a just alias of length. count can accept condition and count on it. So, length or size are prefered when you just need to know the size of an array. count - when you need to count elements by some condition.
If you are talking of arrays, all these terms have different contextual meaning. Read on datastruct