曾经：(indicating that an action once happened in the past or a state once existed, the verb is usu. followed by 过) once；used to例句：我曾经在这里学习过。曾：(indicating that an action once happened in the past or a state once existed) once；used to例句：我还不曾去过北京。曾经：用在动词前面，表示某种动作、行为或情况是以前某段时间存在或发生过的并且不再延续。动词后面往往有助词过。曾：曾经。两者的意思相同，否定形式都是不曾或未曾，没有不曾经的说法。