Sternutation is the formal word for sneeze. When everything is covered with yellow pollen, many people have fits of sternutation. Hand them tissues. You’ll probably never need this word unless you need extra syllables for haiku about spring.
Sternutation is caused by some irritant — dust, animal dander, or smoke, for example — inside the nose, which causes a sudden burst of air from your lungs to escape your nose and mouth in a sneeze. The purpose of sternutation is to clear your nasal passages of foreign substances. Interestingly, sternutation is impossible while you're asleep. The Latin root is sternuere, "to sneeze."