Oído vs. oreja
The Spanish vocabulary for body parts includes two words that refer to 'ear': 'oído' and 'oreja'. The use of these words can sometimes be confusing, as they seem to be interchangeable. However, each word actually refers to a different part of the ear.
Oído
Oído refers to the inner and middle parts of the ear - the internal structures that allow us to hear.
Tengo dolor en el oído.
(I have pain in my ear.)
No puedo escuchar bien, tengo un problema con mi oído.
(I can't hear well, I have a problem with my ear.)
Oreja
Oreja describes the outer part of the ear - the external structure that we can see and touch.
Tu oreja es muy pequeña.
(Your ear is very small.)
Ella tiene un arete nuevo en la oreja.
(She has a new earring in her ear.)
Summary
'Oído' and 'oreja', although used to describe similar areas, point to different components of the human ear. While 'oído' signifies the internal mechanisms responsible for processing sound, 'oreja' refers to the physical exterior structure.