pi·on 
(pīŏn′)
(pīŏn′)n.
Any of the three least massive mesons, having a positive, neutral, or negative electric charge. The charged pions have a mass 273 times that of an electron and a mean lifetime of 2.6 × 10-8 second, and the neutral pion has a mass 264 times that of an electron and a mean lifetime of 8.4 × 10-17 second. Also called pi meson.
[Contraction of PI MESON.]
- Illinoisan
- Illinois River
- Illinois Waterway
- illiquid
- illiquidity
- illiteracy
- illiterate
- illiterately
- illiterateness
- ill-mannered
- ill-manneredly
- ill nature
- ill-natured
- ill-naturedly
- ill-naturedness
- illness
- illness anxiety disorder
- illogic
- illogical
- illogicality
- illogically
- illogicalness
- ill-sorted
- ill-starred
- ill-tempered