The adenoid is a small mass of lymphatic tissue located at the back of the nasal cavity, above the roof of the mouth. It plays a role in the immune system by helping to trap and fight infections, especially in children. The adenoid is part of a group of tissues known as Waldeyer's ring, which also includes the tonsils. In some cases, the adenoid can become enlarged, leading to breathing difficulties, sleep apnea, or recurrent ear infections. This condition is often referred to as adenoid hypertrophy. If symptoms are severe, a doctor may recommend a procedure called adenoidectomy to remove the enlarged tissue.