Laboratory & Lavatory

Laboratory is a place or location specifically designed for and equipped for scientific investigation, research, or study: “The language laboratory of our college is fitted with latest gadgets to help improve the communication skills of the students.”
Lavatory , on the other hand, is a specifically designed room equipped with basins and toilets; often with multiple conveniences: “I felt much irritated and uncomfortable when I did not find any public lavatory near the bus stand.”