A characteristic was a distinguishing feature or quality of a person, place, or thing.
In 2269, while trapped in the Sarpeidon Ice Age time period, Captain James T. Kirk asked Spock if he was in the library, to which his answer was no because they were in a wilderness of arctic characteristics. (TOS: "All Our Yesterdays")
A defining characteristic shared by multiples of the same item was called a hallmark. According to Damar, overconfidence was the hallmark of the Weyouns. (DS9: "Strange Bedfellows")