The majority of tea (pu’erh my beloved excluded) is not fermented it is oxidized.

Fermented: silly lil guys do some magic to make flavour get funky. EX: pu’erh, wine, miso, bread Oxidized: Oxygen, destroyer of worlds, wrecks havoc on the chemical structure of hapless molecules. EX: Guac that has gone brown, green, oolong, and black tea, rust.