This is how you sign Birthday in American Sign Language.
Learn how to sign "Birthday" in American Sign Language(ASL). Take your non-dominant forearm and hold it across your body with palm facing upward. Then, take your open dominant hand and wave it back and forth above your other flat hand. Next, form the letter 'D' with your dominant hand. Place the elbow of your dominant hand on the fingers of your non-dominant hand. Then, move your hand down at the side.