Yeast
A micro-organism that converts the sugar to alcohol in a process known as alcoholic fermentation.

Yield
The amount of fruit any given vine or vineyard produces, and is usually expressed in hectolitres per hectare. Yields vary according to the type of vine - some are heavy croppers, some yield less - and also with climate and soil. Yields may be influenced by the winemaker, who may perform a green harvest on order to reduce them. Low yields are associated with increased quality.

Young
Simple wines signifies youthful freshness. In finer wines, young refers to immaturity.