What is dihydrogen monoxide?

Answer 1

Dihydrogen monoxide is just another name for water. Di-meaning two, and mono- meaning one, translate "dihydrogen monoxide" to the chemical representation, H2O. Other names for water include hydrogen hydroxide, hydrogen oxide, hydroxic acid, hydroxylic acid, and oxidane.

Dihydrogen monoxide has been the subject of many pranks and hoaxes, with claims that it contributes to the greenhouse effect, causes erosion, corrodes metals (i.e. it causes some metals such as iron to rust), is the major component in acid rain (which it is, considering its still rain), lethal if inhaled (partly true if its in liquid form, but the same could be said for oxygen or nitrogen) and as much as a thimble full could be lethal (perhaps if they injected it directly into your brain, or it was a very large thimble.)

These claims present "dihydrogen monoxide" as a dangerous chemical used in nuclear facilities, military installations, industrial plants, and in the manufacture of styrofoam, among other true things. Water is indeed used in many ways, and can pose a health hazard when consumed in exceptionally large amounts, but such "dihydrogen monoxide claims" distort these facts for the purpose of the prank or hoax.