Collection - Sequence (Ordered)

A sequence is an abstract collection:

• of non-unique element
• where order matters - ie (A,B) is not equal to (B,A)

non-unique means that it allows duplicate member (the same element/value may occur more than once).

• (M, A, R, Y) is a sequence of letters with the letter M first and Y last.
• (M, A, R, Y) differs from (A, R, M, Y)

The position of an element in a sequence is its rank or index.

Collection - Cardinality (Size/Length) - In computer science

A finite sequence is called a list

A infinite sequence is called a stream and is generally read through a iterator pattern.

It's a data structures with no or slow random access.

• Sequence