Adenoid lies in the:
Tonsils:-
Collections of lymphoid tissue in the oral, nasal and pharyngeal region.
CLINICAL ANATOMY

Hypertrophy or enlargement of the nasopharyngeal tonsil or adenoids may obstruct the posterior nasal aperture and may interfere with nasal respiration and speech leading to mouth breathing. These tonsils usually regress by puberty.
Hypertrophy of the tubal tonsil may occlude the auditory or pharyngotympanic tube leading to middle ear problems.

Waldeyers tonsillar ring has:-

Adenoid tonsil (or nasopharyngeal tonsils) – in nasopharynx
Two palatine tonsils (or simply tonsils) – in oropharynx b/w palatoglossal and palatopharyngeal arches
Lingual tonsil – Behind terminal sulcus (tongue)  Two tubal tonsils — root of pharynx.

Key Concept:
Adenoid tonsils are also known as nasopharyngeal tonsil, named based on its location.
Hypopharynx
Oropharynx
Trachea
Nasopharynx