Axila vs. sobaco

In Spanish, the words 'axila' and 'sobaco' both mean 'armpit', but they are used in different contexts and can convey different tones.

Axila

This term is considered more formal and is often used in medical, anatomical, and more polite contexts.
El doctor revisó la axila del paciente en busca de hinchazón.
(The doctor checked the patient's armpit for swelling.)
La crema debe aplicarse en las axilas después del baño.
(The cream should be applied to the armpits after bathing.)
Para la clase de anatomía, debemos aprender los músculos de la axila.
(For anatomy class, we need to learn the muscles of the armpit.)

Sobaco

This term is more informal and can sometimes be considered vulgar or colloquial. It's often used in everyday speech and less formal situations.
Hace mucho calor y me suda el sobaco.
(It's very hot, and my armpit is sweating.)
Se me rompió el desodorante antes de aplicármelo en el sobaco.
(My deodorant broke before I could apply it to my armpit.)
Me dolía el sobaco después de hacer ejercicio intenso.
(My armpit was sore after doing intense exercise.)

Summary

'Axila' is the preferred term in formal, medical, and polite contexts while 'sobaco' is suited for informal or colloquial settings. Choosing between these terms depends on the context and tone you wish to convey.