An arithmetic series is the sum of the terms in an arithmetic sequence, where each term increases or decreases by a constant value called the common difference. For example, in the sequence 2, 4, 6, 8, the common difference is 2. The series can be expressed as S = a + (a + d) + (a + 2d) + ... + l, where S is the sum, a is the first term, d is the common difference, and l is the last term. To find the sum of an arithmetic series, you can use the formula S = n/2 × (a + l), where n is the number of terms. This formula simplifies the calculation by averaging the first and last terms and multiplying by the number of terms. Arithmetic series are commonly used in various fields, including mathematics, finance, and computer science, to analyze patterns and make predictions.