The term use to be "female" but change to "feminized" because not all of the seeds will turn out to be female. It all depends on the growing conditions but mostly they will turn out to be female plants.....now that I read my post it doesn't really help you out with your question
You can't tell by looking, just buy them and trust the source is reliable. You have to pay extra close attention to the entire plant and each bud because the feminised have a tendency to hermaphrodite on you, especially if there is any light leakage. You will wind up with both male and female on the same plant and they will pregnant themselves. So you may wind up with buds chock full of seeds.