a sequence of one or more characters within the current locale that collate as if they were a single character.
an unspecified data structure that is used to represent a regular expression, and which permits efficient matches against the regular expression to be obtained.
a sequence of one or more characters that is to be replaced with some part of a regular expression match.
a sequence of zero or more characters is matched by a regular expression when the characters in the sequence correspond to a sequence of characters defined by the pattern.
a set of one or more characters which share the same primary sort key: that is the sort key weighting that depends only upon character shape, and not accents, case, or locale specific tailorings.
a pattern that selects specific strings from a set of character strings.