Ambassador K'Ehleyr is half human & half Klingon. If she were infertile, she would be a hybrid -- the infertile product of a cross of species.
But she had a child with Worf, a Klingon. That means K'Ehleyr is the fertile offspring of a Klingon & a human -- which means they are the same species, by the biological definition of that word.
But she had a child with Worf, a Klingon. That means K'Ehleyr is the fertile offspring of a Klingon & a human -- which means they are the same species, by the biological definition of that word.