(1)不肯定(确知)的(not definitely knowing;not confident or sure)[无comp][通常作pred][A(of/about)]：be～of/about sb's intentions/sb's wishes/sb's legal rights/the truth对某人的意图/愿望/法律权利/事实心中无数;The actor is still～of his words/his ability (to play the part). 这位演员对他的台词/(扮演此角色的)能力还心中无数。I shall certainly be present， but I'm～about my wife. 我肯定要出席，但是至于我的妻子是否出席我说不好。be/feel～(about) what to do不能肯定要做什么/觉得说不好该做什么;The government is～what is the best thing to do. 政府还不能肯定什么是最应该做的事情。Whether the game will be held or not is～. 还不能肯定比赛是否举行。〖同〗unsure，doubtful，indefinite，unconfirmed;〖反〗certain，definite，sure，assured，confirmed，positive;

(2)难以预料的，未知(定)的(not known or established;vague)：The plan for holiday is～.假日计划还未确定。a manuscript of～origin来历不明的手稿;An～number of people were waiting. 一些人正在等侯，人数不详。An～shape loomed ahead in the darkness. 黑暗中赫然出现一个模糊的身影。The outcome of the election is still～. 选举结果仍难以预料。a lady of～age一位无法猜出其年龄的女士;She gave him an ultimatum in no～terms.她断然向他发出最后通谍。〖同〗unpredictable，undetermined，indefinite，indistinct;〖反〗certain，definite，predictable，known，determined;

(3)易变(无常)的，捉摸不定的(subject to change;variable)：a man of～temper喜怒无常的人;The aim is～.目标摇摆不定。 The dog is of～temper. 这条狗脾性多变。U～weather delayed (postphoned) our departure/our beach trip. 变幻莫测的天气拖延(推迟)了我们的离去/海滩旅行。U～people make poor leader. 变化无常的人当不了好领导。〖同〗variable，unsure;〖反〗 certain，definite，firm，resolute，unvarying;

(4)不稳定的，迟疑的(unsteady;fitful)：an～voice/smile含糊的嗓音/勉强一笑;the baby's first～steps 婴儿蹒跚学步;

←′certain adj;

→un′certainly adv犹豫地;un′certainness n变化无常;un′certainty n易变化