Here's why:

* "Snot" is a colloquial term. It's a casual, everyday word.

* Scientifically, it's called mucus. Mucus is a sticky substance found in many bodily fluids, including nasal secretions (what we call snot).

* Nasal mucus is more specific and refers to the mucus produced by the nose.

So, while "snot" is understandable, "mucus" or "nasal mucus" are the more scientifically accurate terms.