Power of alphabet (sigma power n) , is set of all strings of length n for that alphabet.
If alphabet Sigma contains k symbols, then Number of strings in ( ∑ power n) is ( k power n ).
For any alphabet, ∑0 = {ε} .
∑* contains all strings of all lengths.
∑* contains all possible strings over given ∑ .
For any language L over given ∑ , L ⊆ ∑*
∑+ = ∑* − {ε}