Pauillac: One of the four great wine communes of the Medoc peninsula just northwest of the city of Bordeaux along the Gironde River in France. Some say it is the greatest of the four key wine appellations, since so many first growths of the Bordeaux region lie within the Pauillac commune. In fact, lesser regional wines from Pauillac are scarce because most of the wine produced in the region belongs to those famous first growths and is bottled under their names.

Pedro Ximenes: Grape variety used in Spanish sherries, where it often adds sweetness.

Petite Verdot: Grape variety most famous from Bordeaux but used elsewhere also.

PH: a measure of acidity in a wine.

Phenolics: A term to include all of the various types of compounds having the general chemistry of phenols. Grape and wine pigments are phenolics, as is tannin. See polyphenols.

Photosynthesis: The biochemistry that manufactures carbohydrates (sugars) in green tissue of living plants from CO2 and water. The CO2 enters leaves directly from air and the water comes up from the roots. The reaction uses sunlight as its energy source.

Phylloxera: A microscopic aphid that lives on vine roots by sucking their juice. Unfortunately this is never good for roots. The aphid kills European wine varieties but native American vine roots are resistant. Hence most all vines in Europe are grafted on to American root stock – bet you never new that!

Pinot: One of the world's most important family names among the world's wine grape varieties. The most famous member is Pinot Noir, although its white-fruited variant, Pinot Blanc, deserves special recognition as well.

Polyphenols: Chemical class of compounds which occur naturally in wine, giving it an astringent, bitter or mouth-drying taste sensation. Tannins and grape skin pigments are two prominent classes of polyphenols.

Pomace: The solid remains of grapes after pressing for juice.

Port: Any of the rich, sweet, alcoholic and full-bodied wines from the Oporto region of Portugal. Other countries also use the term for wines of similar type, but the original name is Portuguese.

Powdery mildew: A devastating fungal disease of grape vines that, unlike most fungal diseases, thrives in dry climates. Also called odium, it occurs in most of the wine regions of the world. It can be controlled by timely application of sulphur dust directly onto the vine leaves and immature fruit. New fungicides have been introduced in recent years that greatly improve a vine's recovery from severe attacks. See Downey mildew.

Press juice: The juice obtained not by draining but by pressing fresh pomace. It is usually far more tannic (often bitter) than drained or lightly pressed (free run) juice.

Primativo: An Italian grape variety thought to be identical to Zinfandel.

Proof: Scale for measuring and expressing the alcohol content of high alcohol liquids. Proof is never used for wine. The proof of a liquor is twice its alcohol content, i.e., 80 proof = 40% alcohol. Since wine is always much lower in alcohol than the range commonly used for proof, the term has no use in wine production and is not used on wine labels.

Pruning: The act of cutting off various parts of grape vines, usually in winter when the vines are dormant. Pruning develops the shapes of vines when they are young and controls the growth, fruit quantity (and therefore, quality) of producing vines.

Pumping over: The act of pumping wine out from a bottom valve of a fermenting tank up onto the top of the fermenting mass in the same tank to keep the floating "cap" of skins wet. This is necessary during fermentation of red wine in order to achieve complete extraction of colour and flavour from the skins.

Punching down: The act of pushing the cap down into the fermenting liquid to wet it and facilitate colour and flavour extraction. This is the traditional method, but it can only be used for small tanks.

Punt: The concave indentation in the bottom of certain wine bottles, especially those containing sparkling wine. Several reasons for it may be found in literature: to collect crystals or sediment (this only works if the bottle is standing upright) so that the wine may be decanted easily. Today’s wine bottles use the punt for balance i.e. taller or heavier bottles have a larger punt vs. smaller lighter bottles – take a look