Nomos
Part (binomial)
Nova-
New (Nova Scotia)
Nuc-
Nut, kernel (nucleus)
Nul-
Nothing (null set)
Oct-
Eight (octagon)
Oid
Similar (nucleoid)
Oma
Tumor (sarcoma)
Omni-
All (omnivore)
On, ont
Being, object, thing (operon)
Oo-
Egg (oocyte)
Opera
Work (operon)
Ophth-
Eye (ophthalomology)
Organ
Tool, instrument, functional part (organelle)
Osis
Condition (scoliosis)
Osteo-
Bone (osteoporosis)
Oto-
Ear (otitis)
Ovi-
Egg (ovary)
Pan-
Companion (pandemic)
Para-
Beside (parathyroid)
Patho-
Disease (pathology)