• obelisk (†)


• obelism


• object


• object complement


• object pronoun


• oblique (/)


• oblique case


• occlusive


• OED


• officialese


• officious | official


• of-genitive


• Ogden, C.K.


• Ogham


• Oh | O


• Old Church Slavonic


• Old English


• Old French


• Old High German


• Old Low German


• Old North French


• Old Saxon


• oligosynthetic language


• onomasiology


• onomasticon


• onomastics


• onomatechny


• onomatology


• onomatopoeia


• onomatopoeic coinage


• onomatotechny


• onset


• open-class item


• open word class


• optative mood


• ordinance | ordnance


• oronyms


• orthoepy


• orthographic depth


• orthographic principle


• orthography


• ostensive definition


• OV language


• Oxford comma


• Oxford English Dictionary


• oxymoron