Arithmetic sequence- the difference between one term and the next is a constant.

Arithmetic series – the sum of the arithmetic sequence.

Common difference (d) – the constant value.

Geometric sequence – formed by multiplying each term after the 1st term by a constant.

Geometric series – the sum of the terms of a geometric sequence.

Common ratio (r) – the constant. To get the common ratio divide the second term by the first term.