1. Feeling miserable and apathetic
   - mopey

Derived forms: mopier, mopiest

• ontology
• onus
• onward
• onward motion
• onwards
• onya
• onycha
• Onychium
• Onychogalea
• onycholysis
• Onychomys
• Onychophora
• onychophoran
• onychosis
• onymous
• onyx
• onyx marble
• onyxis
• oocyte
• oodles
• oogenesis
• ooh
• oolite
• oology
• oolong