What evidence must be considered when determining whether or not a trait is an adaptation

An adaptation can be viewed as a trait that emerged and developed for a certain condition so as to increases the organism changes of survival or fitness.

For a trait to be called adaptive, it must have had a positive influence but not majorly a trait that develops in reaction to a certain selection pressure.

Categorically, a trait is seen as adaptation if it is the aftermath of selection, and adaptive if it is of favourable influence at the existing time.