Describes one of the four basic tastes (along with sour, salty and sweet). Some grapes--notably Gewürztraminer and Muscat--often have a noticeable bitter edge to their flavors. Another source of bitterness is tannin or stems. If the bitter quality dominates the wine's flavour or aftertaste, it is considered a fault. In sweet wines a trace of bitterness may complement the flavors. In young red wines it can be a warning signal, as bitterness doesn't always dissipate with age. Normally, a fine, mature wine should not be bitter on the palate.