A trait is formally defined as
trait. A characteristic or condition that is determined by one's genes. The color of an animal's coat and the shape of a plant's leaves are physical traits. Nesting in birds and burrowing in rodents are examples of behavioral traits.- A stroke of a pen or pencil.. a distinguishing characteristic or quality, esp. of one's personal nature: bad traits. 2. an inherited feature or characteristic: a recessive trait. 3. a pencil stroke. 4. a touch or trace. tractus.