prevail是流行盛行的意思，其名词形式为prevalence.
名词形式为prevalence，例如：
1.Despite its prevalence, schizophrenia has existed behind a wall of secrecy for years.尽管精神分裂症患者为数众多，但多年来这种病一直被捂着掩着。
2.Method: We had made a prevalence survey through a questionnaire.方法：采用自填问卷进行现况调查。
3.Prevalence features of chronic kidney disease in new stroke of 567 patients.567例新发脑卒中慢性肾脏病流行病学特点。
