based on random choice or personal whim, rather than any reason or system
随机选择的,随心所欲的,无理由的,无系统的
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his mealtimes were entirely arbitrary. 他吃饭完全不定时。
 
(of power or a ruling body)unrestrained and autocratic in the use of authority
(权力,统治机构)专断的,专制的
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a country under arbitrary government. 一个受专制政府管理的国家。
 
【数】 (常数,量)任意的。
"late Middle English (in the sense ‘dependent on one's will or pleasure, discretionary’):  from Latin 



