Pls get to know that the two items are totally different. Now and here I will tell you some easy way to distinguish these two words. You can now look at your own eyes in the mirror; the pupil is the black hole in the center of the eye, and the iris is the colored circle, which surround the pupil. Of course, you can get to know the difference by the function of the two parts of eyes. The pupil has the function of allowing the light outside to enter the eye. However, the iris is just a muscle controlling the size of the pupil so that the iris can limit the amount of the light entering our eyes. The iris plays an important role in our eyes, namely, if too much light enters into your eye, which will result in the hurt of light sensitive proteins; if you do not get enough light, you will not see clearly, when your pupil will get larger or dilate in low light.
Yes, I also heard someone saying that the black spot in the eyes is called the iris. However, there exists the difference between the iris and pupil. The iris is a thin diaphragm composed mostly of connective tissue and smooth muscle fibers. The pupil is a hole located in the center of the iris of the eye that allows light to enter the retina. In addition, the pupil may get dilated because of the shocking or surprising situation. If you find something interesting, your eyes may get dilated too. However, if you smoke or drink too much, the dilated pupils may be bad for the eye health. You'd better protect the eyes carefully.
The iris is a patch of tissue on your eye, which is like a curtain. It is the colored part of the eye around the pupil, which is typically brown or blue. And pupil is the gap between the tissue on your eyes. It looks like a black dot in the center of the iris. It can dilate and contract. The size of the pupil changes totally depends on how bright the light is.