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The systematic or IUPAC name for the chemical commonly known as acetic acid, viz the basis of vinegar, chemical formula CH3COOH.

The eth- indicates that it has two carbon atoms (meth- = 1, eth- = 2, prop- = 3, but- = 4, then Greek words from pent- = 5 onwards). The -an- indicates that the bond between carbons is a single bond (-an- = 1, -en- = 2, -yn- = 3), though in this particular molecule all the valencies are already claimed and no double bond could exist. The -oic acid indicates that it is a carboxylic acid, that is of the form RCOOH for some radical R.

This name is used, particularly in schools material, it seems. I was taught systematic naming in school. However, at about 3500 Google hits to 130 000 for the common name acetic acid, it's got a long way to go.