Starter - a stable culture of natural yeast and lactobacilli maintained over time, propagated and continued for the purpose of leavening.

Refresh (Feeding) - Feeding a starter, adding nutrients in the form of flour and water to re-activate the starter and bring its leavening and flavouring microbes to peak levels of activity.

Refrigerator Starter - Starter that is stored in the refrigerator most of the time and is taken out refreshed and fully activated prior to mixing final bread dough (also known as Mother or Storage Starter).

Pre-ferment - This term refers to any mix or Starter that is allowed to ferment and build its leavening ability prior to being incorporated into final bread dough. This includes both yeasted and naturally leavened Starters. A pre-ferment contributes leavening and flavour to bread by allowing the dough longer periods of fermentation, which enhances the texture, and flavour of the bread.

Sourdough Bread - bread that has been leavened by a sourdough Starter. Sourdough bread may or may not have a sour flavour depending on the acids produced by the specific strains of lactobacilli that are involved in the fermentation process. Sourdough bread is not necessarily sour bread although it can be.

Sour bread - Bread dough, which has an acid pH and a sour flavour, caused by either natural leaven fermentation (sourdough) or through the addition of souring agents such as yogurt, vinegar or various souring salts. Sour bread is only sourdough bread when it has been leavened by a sourdough (natural leaven) culture of wild yeast and lactobacilli.

Fully Activated - that stage in the cycle of a starter of peak yeast and lactobacilli activity. A fully activated starter is full of large and small bubbles which are well-integrated throughout the starter (not just on top), there may be a layer of foam or froth on the very top and if the starter is a thick enough batter, it will have increased in volume by double or more.

Leaven - a leavening agent (sometimes called just leavening or leaven) is a substance used in dough's and batters that causes a foaming action. The leavening agent reacts with moisture, heat, acidity, or other triggers to produce gas that becomes trapped as bubbles within the dough. When a dough or batter is baked, it "sets" and the holes left by the gas bubbles remain, giving breads, cakes, and other baked goods their soft, sponge-like textures.

Natural Leaven - a piece of final dough saved from one bake to the next. It differs from a starter only in that it is saved after the final dough has been mixed and therefore contains salt.

Old dough can be used to leaven fresh dough. Depending on its age it may need to be either refreshed in order to strengthen its leavening ability or additional leavening may be used along with the old dough.

Fermentation (of bread) - the process by which bread is leavened, also known as "rising". As the simple sugars are broken down from starch in flour, the micro organisms in bread dough feed and then release various metabolic by-products (carbon dioxide, alcohol, organic acids and organic volatiles), which flavour the bread and cause it to rise.

Natural Fermentation - this term refers to any process that uses a Starter that is allowed to ferment and build its leavening ability prior to being incorporated into final bread dough. The natural fermentation contributes leavening and flavour to bread by allowing the dough longer periods of fermentation, which enhances the texture, and flavour of the bread.

Yeast - yeast is a fungus, a member of the plant family. Yeast exists on plants, in the air, in soil, and in and on humans and animals. Yeast metabolise simple sugars and produce alcohol and carbon dioxide through the process of fermentation. Different strains of yeast are used for different processes, such as brewing and dough rising.

Bakers Yeast - in the 1860's Louis Pasteur discovered how bread is leavened and how yeast "works". A particular strain of yeast named Saccharomyces cerevisiae was found to be an excellent leavener for bread and one that could be easily manufactured. Whether you use fresh (compressed) or dry yeast (either regular active dry yeast or instant dry yeast), you are using strains of Saccharomyces cerevisiae that have been engineered, manufactured and packaged for commercial and home use to be predictable, reliable and fast-acting.

Levain - a French word for a natural leaven mixed to a dough-like consistency. A levain is made by adding flour and water or just flour to a "Chef". This process is referred to as "building" or "elaborating" the next stage of the leaven. A levain or levain bread dough is generally fermented at cool temperatures. The firmer consistency and cool temperature fermentation of a levain promotes the development of Lactic rather than acidic acids, and bread leavened with a levain (Pain au Levain) has a rich, complex flavour and is generally not sour.

Chef - A French word for a natural leaven starter which is retained and used from bake to bake. Sometimes it refers to a piece of old dough saved off for the next bake, sometimes to a starter in its first stage, either a batter- or dough-like consistency. In classic French baking a "chef" is "built" (or "elaborated") into a "levain" (a firm dough-like consistency), which is again built (or elaborated) into leavening for final bread dough.

Sponge - A pre-ferment of a wet rather than firm (dough-like) consistency. It is a mixture of leavening (either commercial bakers' yeast or natural leavens), liquid and flour mixed prior to the final bread dough and allowed to ferment anywhere from a few minutes to 24 hours (or more). Used to improve the flavor and texture of bread dough and to build leavening strength.

Poolish - A French term for a sponge, a mixture of commercial bakers yeast, water and flour. Usually a wet mixture rather than firm. Classically the water and flour are in a 1:1 ratio by weight although in common use the term now equates to "sponge"

Biga - an Italian word for a yeasted starter. To make a biga, a tiny amount of commercial bakers yeast is mixed with water and flour to a dough-like consistency and fermented for a long period of time, 12 to 24 hours or more. It is then mixed into bread dough for leavening, often with the addition of more commercial bakers' yeast.

Proofing - (also called proving) is a step in creating yeast breads and baked goods where the yeast is allowed to leaven the dough. During proofing, yeast converts glucose and other carbohydrates to carbon dioxide gas which gives the bread rise and alcohol which gives it flavor. Bacteria which coexists with the yeast consume this alcohol, producing lactic and acetic acids.

Dough proofer - is a chamber used in baking that encourages fermentation of dough through warm temperatures and controlled humidity. The warm temperatures increase the activity of the yeast, resulting in increased carbon dioxide production and a higher, faster rise.

Dough retarder - is a refrigerator used to control the fermentation of yeast when proofing dough. Lowering the temperature of the dough produces a slower, longer rise with more varied fermentation products, resulting in more complex flavours. In particular, cold temperatures reduce the activity of the yeast relative to the lactobacilli, which produce flavouring products such as lactic acid and acetic acid.

Banneton - is a type of basket used to provide structure for the sourdough breads during proofing. Proofing baskets are distinct from loaf pans in that the bread is normally removed from these baskets before baking. These baskets are used both to provide the loaf with shape and to wick moisture from the crust.

Couche - or proofing cloth, are generally made of linen so the dough will not stick. Couches are left unwashed for long periods so as to let yeast and flour collect in them, aiding the proofing process.