areola

noun5

1. •
   The circular, darkly pigmented area surrounding a nipple; the areola mammae.
2. •
   Any small circular area that is different from its immediate environment, such as the colored ring around the pupil of the eye (iris) or an inflamed region surrounding a pimple.
3. •
   Small patches, bearing the spines and glochids characteristic of the stems of cacti.
4. •
   Any of the small spaces throughout areolar connective tissue.

   • The tubes or elongated spaces of which we have spoken, are not distended with any fluid, but are merely moistened in the same way as the areolas of ordinary areolar tissue. — 1847
5. •
   Any of the small spaces between fibres of the tissues of certain lichens.