null - oner
- on option
- on or about
- on or about the person
- on or before
- on or in or about
- on or upon the death
- on peut bien receivoir loy d'autruy, mais il est impossible par nature de se donner loy
- on sale
- on sight
- on the account
- on the body
- on the death
- on the front
- on the merits
- on the relation of
- on trial
- on-the-spot broadcast
- onanism
- once a highway, always a highway
- once a mortgage, always a mortgage
- once a week for four successive weeks
- Once an Englishman always an Englishman
- once in jeopardy
- one bite rule
- one dollar
- one dollar and other consideration
- one dwelling
- one free bite
- one half
- one man-one vote rule
- one residence
- one residence only
- one third new for old
- One who institutes suit against another must be prepared to show a prior or superior equity in himself
- One who invites another to ride is not bound to furnish a sound vehicle or a safe horse
- one-family house
- one-man car
- one-man corporation
- one-price policy
- one-way street