A full stop.
No, "sign language" is not typically capitalized in a sentence unless it is part of a title or at the beginning of a sentence.
Will will sign the will.
It should be --- Then I said, "Why do I sign?"
A mathematical sentence that contains an equals sign would be called an equation.
No, the finger spelled alphabet does not have capitalized versions of the letters.
A mathematical sentence that uses an equal sign to explain the equality of two amounts is called an equation.
doesn't
Example sentence - The road sign gave the mileage to the next three cities.
He gave me a sign to come over.I will sign to her.You need to sign this paper.
sign
yes you can, eg I like to sign cards.
a number sentence.