a list of acceptable characters for the next single character of the matched string
a list of symbols between square brackets and matches any single character that matches on of the symbols inside the brackets
an expression that matches one of a defined set of characters
an item in a pattern that can match any character in a specific set
a series of characters, any one of which is a valid match for that position
a set of characters enclosed in square brackets
a set of characters enclosed within square brackets
A regex construct that identifies a set of characters between open and close square bracket metacharacters ().