Attenuation is the amount of sugars converted into alcohol and carbon dioxide by yeast, usually expressed as a percentage. Attenuation figures can be expressed as "Apparent" or "Real" due to the fact that alcohol is less dense than water. A 1.050 wort fermented to 1.012 has an Apparent Attenuation of 75%, but a Real Attenuation of 63%.

Further Reading

• Understanding Attenuation