Gene gave a good answer- thanks for that Gene.
As with so many of these questions, you need to specify by what definition a question is being answered. MLS rules are one definition, and they differ from state to state and from system to system.
Local city, township or building codes also give especific definitions of what qualifies to be classified as a bedroom, or something else. --and also vary widely in their descriptions.
Many areas now use the Universal Building COde-- which helps! Ask what the rules are in the city or township or county where the property is located.
Hope that helps.