=nŏce-o=, _I harm_; =nox-ius=, _hurtful_: in-noc-ent, innocuous, noxious, nuisance.
=norma=, _a rule_; root nō- as in _nōtus_: normal, abnormal, enormous.
=nota=, _a mark_; =nŏt-o=, (nŏtāt-), _I mark_: note and notable (Fr.), notary.
=nŏvus=, _new_; =nuntius=, _news_: novel and novice (Fr.), in-nov-ation, denunciate, an-nunciation = announcement (Fr.), pronounce (Fr.).
=nox= (noct-), _night_: noct-urnal, equi-nox, equinoctial.
=nūbĕre= (nupt-), _to marry_: con-nubial, nuptial.
=nutri-o= (nutrīt-), _I nourish_; =nutrix= (nutrīc-), _a nurse_: nutri-ent, nutri-ment, nutritious; through Fr., nurse, nursling, nourish, nurture.
=Ŏculus=, _eye_: ocular, oculist, ocellus.
=omnis=, _all_: omnibus, omni-scient, omnipotent.
=ŏnus= (ŏnĕr-), _burden_: onerous, ex-onerate.
=ops=, _means_; =ōptimus=, _best_: opulent, optimist, optimates.
=ŏpus= (ŏpĕr-), _work_; =ŏpĕra=, _service_: operate, operative, co-operation, opera.
=opt-o= (optāt-), _I desire_: option, adopt, adoptive, optative.
=ordo= (ordĭn-), _order_, _row_; =ordĭn-o= (ordĭnāt-), _I set in order_; =orno= (ornāt-), _I deck_: ordinal, extra-ordinary, ordination, co-ordinate, in-subordination, orna-ment, ad-orn, ornate; through Fr., order, ordain.
=oriens=, _rising_ (=sōl oriens=, _the east_); =orīgo= (orīgĭn-), _source_: orient, orientalist, orientation, origin (Fr.), originality.
=ōs= (ōr-), _mouth_; =ōr-o= (ōrāt-), _I speak_, _pray_; =ōmen= (omin-), _token_: oral, or-acle, o-rotund, ori-fice (_facio_), os-cul-ation, adore, oration = orison.
=ōvum=, _egg_; =ōvātio=, _an ovation_: oval, ovary, ovi-form, ovi-parous (_pario_).
=Paenīt-ēre=, _to be sorry_: through Fr., penitent, repentance, penance.
=pāgus=, _country district_: pagan, page (boy) and peasant (Fr.).
=par=, _equal_: parity; through Fr., pair, peer, compeer, dis-parage, um-pire.
=păro= (părāt-), _make ready_: com-par-able, ap-paratus, pre-paration; through Fr., repair, reparation, comparison, parry, parade, para-sol (Port.).
=pār-ēre=, _be visible_: ap-parent; through Fr., appear, peer (= to peep).
=pars= (part-), _part_; =partīt-us=, _divided_: partitive, partition, participate (_căpio_); through Fr., part, parcel, partner, parse.
=pătēre=, _to be open_; =pandĕre= (pans-, pass-), _to extend_: patent, paten, patella = pail (Fr.), expand; through Fr. pass, passage, pace, pan.