Is it pink eye, conjunctivitis or blepharitis?

Conjunctivitis: " pink eye" generally is considered an infection of the eye causing inflammation of the lining or conjunctiva. Hence conjunctivitis.

Could be any of them: The etiology (cause) of a "red eye" could be: (1) classic "pink eye" as it is referred to by the lay population. This is really a viral conjunctivitis, which just means there is inflammation of the lining of the surface of the eye (conjunctiva) caused by a virus - like a "cold" in the eye. (2) conjunctivitis - the general term defined above. (3) blepharitis, or inflammation of the eyelid margins.