Meaning of L* if L is a language
Given a language $L$, let $L_0 = \{\epsilon\}$ and, for $i\geq 1$, let $L_i = \{w_1\circ \dots\circ w_i \mid w_j\in L \text{ for each } j\}$, where $\circ$ denotes concatenation.  Then the Kleene closure of&nbsp;$L$ is the language $L^* = \bigcup_{i\geq 0} L_i$.