We call more than one of these "phenomena" (not "phenomenons"). You might call things phenomena if you're studying them closely or scientifically, paying attention to how they move, change, or work, so that you can understand what causes them.
For example, allergic phenomena are the things your body does to freak out when it comes into contact with certain materials. Lisa's nose is red and runny when she's outdoors, breathing in the grass and the flowers. She has allergies, and her red, runny nose is an allergic phenomenon: a thing that her body does in this specific situation.
We tend to pay a lot of attention to phenomena that are amazing and mysterious: rainbows arcing across the sky, stars exploding in space as they die, an athlete leaping through the air to dunk a basketball.