ra·di·o·i·so·tope 
(rā′dē-ō-īsə-tōp′)
(rā′dē-ō-īsə-tōp′)n.
A naturally or artificially produced radioactive isotope of an element.
- offscreen
- off-season
- offset
- offset printing
- offshoot
- offshore
- offside
- offsides
- offsite
- off (someone's) back
- off someone's back
- off (someone's) case
- off someone's case
- off-speed
- offspring
- offstage
- off-the-books
- off the cuff
- off-the-cuff
- off the grid
- off-the-grid
- off the ground
- off the hook
- off-the-rack
- off the rack