What's the difference between twenty and vicennial?

Twenty

Definition:

(a.) One more that nineteen; twice; as, twenty men.
(a.) An indefinite number more or less that twenty.
(n.) The number next following nineteen; the sum of twelve and eight, or twice ten; twenty units or objects; a score.
(n.) A symbol representing twenty units, as 20, or xx.

Example Sentences:

(1) One hundred and twenty-seven states have said with common voice that their security is directly threatened by the 15,000 nuclear weapons that exist in the arsenals of nine countries, and they are demanding that these weapons be prohibited and abolished.
(2) Twenty-seven patients were randomized to receive either 50 mg stanozolol or placebo intramuscularly 24 h before operation, followed by a 6 week course of either 5 mg stanozolol or placebo orally, twice daily.
(3) Twenty patients with non-small cell bronchogenic carcinoma were prospectively studied for intrathoracic lymphadenopathy using computed tomography (CT) and magnetic resonance imaging (MRI).
(4) Twenty volunteers were used for the measurement of pedal pressures for 15 trials during three separate sessions.
(5) One hundred and twelve dogs, including twenty C3-deficient dogs, were studied over a period of 6 years.
(6) Twenty-nine patients had a marked organic tricuspid valvular disease.
(7) Four hundred and twenty-five lesions were dilated in 370 patients.
(8) Striated muscle fibres were found in each of twenty consecutive pineal glands cultured from individual neonatal rats.2.
(9) Twenty-seven human septums were removed at post mortem, examined macroscopically, sectioned coronally and examined microscopically.
(10) Twenty-one patients received 4.5 mg. per kilogram of intramuscular lidocaine and 25 patients received placebo in the deltoid muscle within 14 hours of the onset of symptoms.
(11) Twenty strains did not agglutinate with commercial serum O-Yersinia IMUNA; they were included in the group "Yersinia enterocolitica other biovars" and 60 strains were "Environmental Yersinia isolates".
(12) The results showed that twenty-eight bands were significantly rearranged (P less than 0.05).
(13) Twenty cases of advanced testicular tumors treated primarily by PVB therapy were reviewed.
(14) Lipoprotein(a) was discovered by chance by Berg in 1963; after twenty years of research, the chemical, physical and metabolic characteristics of Lp(a) are now known.
(15) Four of 18 patients showed no change over the twenty-four hours while 7 patients showed some variation without definite diurnal pattern.
(16) Heptathletes peak in their mid-to-late twenties – two Olympic cycles away yet for Johnson-Thompson – so what would she like to achieve in London?
(17) Twenty-nine deletion breakpoints were mapped in 220 kb of the DXS164 locus relative to potential exons of the Duchenne and Becker muscular dystrophy gene.
(18) Twenty-six contacts of 21 families were vaccinated, usually within three days after onset of the index cases.
(19) Twenty patients with central retinal vein occlusion were randomly divided into two groups in a prospective study to evaluate the effects of xenon are photocoagulation in central retinal vein occlusion.
(20) The twenty-five participants, from four different countries, were asked to rate each TC regarding its importance for teachers and whether they possessed them or needed further training.