enter: the most general of these, may imply either going in or forcing a way in: ~ed the city in triumph.


penetrate: carries a strong implication of an impelling force or compelling power that achieves entrance: no bullet has ever ~d a vest of that material.     PEL词根表示to move, drive推动推进        achieve成就成功，表示困难费力


pierce: adds to penetrate a clear implication of an entering point or wedge: a fracture in which the bone ~s the skin.   wedge楔子，一边厚一边薄的工具，用来分离物体


probe: implies a penetration to investigate or explore something hidden from easy observation or knowledge: ~d the depth of the sea.    央视《新闻调查》的英文名是news probe，取其investigate的意思     probe和problem源自同一个词根PROB表示to prove证明，又如probation试用期缓刑期


enter进入: 最通用，可指普通进入或强行进入，penetrate穿入: 表示强大推进力，克服阻力进入，pierce刺入: 强调切入点或线，probe调查探索: 为了调查研究隐秘难观察的事物而进入


记忆方法: 1）首字母EPPP中3P想成三人，E想成进入<==进入

              2）进入的意思是进到里边mean to make way into something.