1. A small grain or pellet; a particle.
2. Geology A rock or mineral fragment larger than a sand grain and smaller than a pebble, between 2 and 4 millimeters in diameter.
3. Astronomy One of the small, transient, luminous markings in the photosphere of the sun.
4. Biology A cellular or cytoplasmic particle, especially one that stains readily.
[Late Latin grānulum, diminutive of Latin grānum, grain; see gə-no- in the Appendix of Indo-European roots.]
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