The common characteristic of the samples in which an ampersand (&) is used is not touching.
What is an ampersand?
The ampersand is the logogram &, representing the conjunction "and".
It originated as a ligature of the letters et—Latin for "and" That definition is how the ampersand is most commonly used today — as an inclusionary symbol meaning “and.”
The term ampersand is a corruption of and (&) per se and, which literally means "(the character) & by itself (is the word) and."
The symbol & is derived from the ligature of ET or et, which is the Latin word for "and."
The common characteristic of the samples in which an ampersand (&) is used is not touching.