pro·ti·um 
(prōtē-əm, prōshē-)
(prōtē-əm, prōshē-)n.
The most abundant isotope of hydrogen, H-1, having one proton and no neutrons in the nucleus.
- open meeting law
- open mike
- open-minded
- open-mindedly
- open-mindedness
- open-mouthed
- open-mouthedly
- openness
- open (one's) eyes
- open one's eyes
- open-pollinate
- open-pollination
- open season
- open secret
- open sentence
- open sesame
- open shop
- open-source
- open stock
- open system
- open universe
- open up
- openwork
- opera
- opera