The BJCP style guide says: A very dark, moderately strong, roasty ale. Tropical varieties can be quite sweet, while export versions can be drier and fairly robust. Roasted grain aromas moderate to high, and can have coffee, chocolate and/or lightly burnt notes. Fruitiness medium to high. Some versions may have a sweet aroma, or molasses, licorice, dried fruit, and/or vinous aromatics. Stronger versions can have the aroma of alcohol (never sharp, hot, or solventy). Hop aroma low to none. Diacetyl low to none. Read More