ac·ti·non 
(ăktə-nŏn′)
(ăktə-nŏn′)n.
A radioactive isotope of radon, Rn-219, having a half-life of 3.96 seconds and produced by the disintegration of actinium.
[ACTIN(IUM) + -ON2.]
- fallibleness
- fallibly
- fall in
- falling action
- falling-out
- falling rhythm
- falling star
- falling tide
- fall into line
- fall in with
- fall line
- fall off
- falloff
- fall on
- fall on deaf ears
- fall on (or upon)
- fallopian tube
- Fallot's tetralogy
- fall out
- fallout
- fall over
- fall over backward
- fall over backward/backwards
- fall over backwards
- fall over (oneself)