A sequence of numbers in which the next term is obtained by adding a constant ‘d’ to the previous term is known as an arithmetic sequence or arithmetic progression.
The following sequence is an arithmetic sequence : 4, 9, 14, 19, 24.
The first term of this sequence is 4 and subsequent terms are obtained by adding 5 to the previous term.
The constant ‘d’ that is added to each term is know as the common difference of the Arithmetic Sequence. It is called the common difference as the difference between any two consecutive term of the sequence is the same.
So, an arithmetic sequence may also be defined as one in which the difference between any two consecutive terms is the same.