Power of alphabet

Power of alphabet: It Σ is an alphabet we can express the set of all string of a certain length from that alphabet by using exponential notation. We define Σ^K to be the set of string of length K, each of whose symbols is in Σ.
Example: Σ⁰ = {ϵ}, regardless of that alphabet Σ is that is ϵis the only string whose length is zero.
If Σ = {0, 1} then Σ¹ = {0, 1}, Σ² = {00, 01, 10, 11} Σ³ = {000, 001, 010, 011, 100, 101, 110, 111} and so on.