{a}
{ ∈ , a, b }
{a, b}
{ ab }
{ a, b, ab, aa }
{ a, b, ba, bb }
{ a, b }
{ aa, ab, ba, bb }
a | b
(ab)*
(a | b)*
a*| b
(0 | 1) *
(0 | 1) (0 | 1)*
(00 01 1 10)*
(0 | 1 ) (0 | 1)(0 | 1) *
with zero or more instances of a or b
with one or more instances of a or b
equal to regular expression (a* b*)*
both 1) with zero or more instances of a or b and 2) equal to regular expression (a* b*)*