-ule Also -ulum, and -ulus.
[Latin endings -ulus, -ula, -ulum.]
Many words in -ule were created in Latin as diminutives, though this sense is often not present in modern English terms derived from them, as with schedule (Latin schedula, a slip of paper, a diminutive of scheda, paper); or ferrule (Latin viriola, a diminutive of viriae, bracelets). Some where a sense of smallness persists are globule (Latin globulus, diminutive of globus, a spherical object or globe), a small round particle of a substance; capsule (Latin capsula, diminutive of capsa, a case), a small case or container; and molecule (Latin molecula, diminutive of moles, mass), a group of atoms bonded together.
Words in -ulum derive from Latin neuter nouns: pendulum (literally, ‘a little hanging thing’ from Latin pendulus, hanging down); curriculum (Latin curriculum, course, racing chariot, from currere, to run); pabulum (Latin, derived from pascere, to feed), bland or insipid intellectual fare or entertainment. Words in -ulus are similarly from Latin masculine nouns: stimulus is from the Latin word meaning a goad, spur, or incentive; cumulus, a type of cloud, derives from the Latin word for a heap; homunculus (diminutive of Latin homo, homin-, man) is a very small human or humanoid creature. Other examples in both endings are mostly specialist words in the sciences.
See also -ole2.