What Vietnamese term in pho ordering means beef ball?

The Vietnamese term in phở ordering that means beef ball is bò viên.

The phrase combines bò, meaning beef or cow, with viên, meaning a ball or rounded piece. On a menu, phở bò viên is phở served with Vietnamese beef meatballs; phở tái bò viên adds rare sliced beef as well.

Bò viên is one of several common topping terms. Nạm usually refers to flank or brisket, gân to tendon, and sách to tripe. Those words identify different beef cuts or parts, not meatballs.

The meatballs are typically springy and firm, made from seasoned beef that is finely ground or pounded. They are added to the hot broth shortly before serving, where they warm without losing their characteristic chewy texture.