[mass noun]absolute certainty or conviction that something is the case 确信,确定无疑 the question may never be answered with certitude. 这个问题从未被确定无疑地回答过。 ■[count noun]something that someone firmly believes is true 深信不疑的事,确定的事
语源
late Middle English: from late Latin certitudo, from certus 'certain'