An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

1) Geology: A term used for a sedimentary particle that is between 2 and 4 millimeters in size. Granules are larger than → sand but smaller than → pebbles. Granules have typically been rounded by abrasion during sedimentary transport (geology.com/dictionary).
2) One of the → convective cells constituting the solar → granulation.

→ grain + → -ule.