title_body: What specific characteristics distinguish an imperial stout from other kinds of stouts?
upvoted_answer: The first Imperial Stout was made by Thrale's Brewery to export to the Russian royalty, it had high alcoholic content so that it could survive the trip gracefully [1]. Since then Imperial has been used as a prefix to signify beers which are of higher alcohol volume than their normal variants, and luckily they're no longer just for Russian royalty.