1 [abc] a, b, or c (simple class) 2 [^abc] Any character except a, b, or c (negation) 3 [a-zA-Z] a through z or A through Z, inclusive (range) 4 [a-d[m-p]] a through d, or m through p: [a-dm-p] (union) 5 [a-z&&[def]] d, e, or f (intersection) 6 [a-z&&[^bc]] a through z, except for b and c: [ad-z] (subtraction) 7 [a-z&&[^m-p]] a through z, and not m through p: [a-lq-z](subtraction) X? X, once or not at all X* X, zero or more times X+ X, one or more times X{n} X, exactly n times X{n,} X, at least n times X{n,m} X, at least n but not more than m times Reluctant quantifiers X?? X, once or not at all X*? X, zero or more times X+? X, one or more times X{n}? X, exactly n times X{n,}? X, at least n times X{n,m}? X, at least n but not more than m times Possessive quantifiers X?+ X, once or not at all X*+ X, zero or more times X++ X, one or more times X{n}+ X, exactly...