(related to Definition: Strings (words) over an Alphabet)
Let $\Sigma:=\{a,b,c\}$ be our alphabet. Then
$a,$ $aa$, $aaaa$, $bca$, $acc$, $aabbcc$, $bbbaaa$,
are possible strings in $\Sigma^*$.
Let $\Sigma$ be the set of all Capital and lowercase Latin letters, including the empty space, the comma, the point, the question mark, and the exclamation mark. Then $\Sigma^*$ consists of (infinitely many) sentences, which can be written using the Latin letters, some of them making sense like
"Socrates is a man."
some of which without any sense like
"DLdfa hidb!zw. alsei?"
Let $\Sigma:=\{0,1,2,3,4,5,6,7,8,9,+,=\}$. Then these are examples of possible strings over this alphabet:
$1=1$, $1=0$, $1+1=2$ $=32$ $===$ $30014$ $2222=333=+++$
Examples: 1