Substring

A substring of a string ${\displaystyle S}$ is another string ${\displaystyle S'}$ that occurs "in" ${\displaystyle S}$. For example, "the best of" is a substring of "It was the best of times". This is not to be confused with subsequence, which is a generalization of substring. For example, "Itwastimes" is a subsequence of "It was the best of times", but not a substring.

Prefix and suffix are special cases of substring. A prefix of a string ${\displaystyle S}$ is a substring of ${\displaystyle S}$ that occurs at the beginning of ${\displaystyle S}$. A suffix of a string ${\displaystyle S}$ is a substring that occurs at the end of ${\displaystyle S}$.

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