More than 70 million Deaf people worldwide use sign language as an official language. Each country has its own sign language, such as American Sign Language in the United States and British Sign Language in the United Kingdom.

No, sign language is not universal. There are different sign languages used around the world, each with its own grammar and vocabulary. For example, American Sign Language (ASL) is different from British Sign Language (BSL) or Australian Sign Language (Auslan).

No, it is more appropriate to say "communicate in sign language" as sign language is a visual-gestural language and not spoken.

No, flipping someone off is not a part of formal sign language used by the Deaf community for communication. It is considered offensive and disrespectful in most cultures and is not used as a gesture in sign language.