vi·cen·ni·al 
(vī-sĕnē-əl)
(vī-sĕnē-əl)adj.
1. Happening once every 20 years.
2. Existing or lasting for 20 years.
[From Late Latin vīcennium, period of twenty years : Latin vīciēns, twenty times (from vīgintī, twenty; see VICENARY) + Latin annus, year; see at- in the Appendix of Indo-European roots.]
- carbon copy
- carbon cycle
- carbon-date
- carbon dating
- carbon dioxide
- carbon disulfide
- carbon fiber
- carbon footprint
- carbonic acid
- carbonic acid gas
- Carboniferous
- carbonium ion
- carbonization
- carbonize
- carbonizer
- carbon monoxide
- carbon nanotube
- carbon-neutral
- carbon-nitrogen-oxygen cycle
- carbonous
- carbon paper
- carbon process
- carbon star
- carbon tetrachloride
- carbonyl