Definitions of rational:

• adjective:   having its source in or being guided by the intellect (distinguished from experience or emotion)

  Example: "A rational analysis"

• adjective:   consistent with or based on or using reason

  Example: "Rational behavior"

• adjective:   capable of being expressed as a quotient of integers

  Example: "Rational numbers"

• adjective:   of or associated with or requiring the use of the mind

  Example: "The triumph of the rational over the animal side of man"