outer: tends to retain its comparative force and apply to what is farther out from something described as inner: the ~ layer of skin is called the epidermis; or is farther than another thing from a center: shed one's ~ garments.    （又如outer space/wall/suburbs/Mongolia外太空/墙/远郊/外蒙古，superlative最高级是outermost最靠外最远的，如the outermost planet in our solar system太阳系最远(靠外)的行星是Pluto冥王星）


outward: commonly implies motion or direction away from, or the reverse of, what is inward: given to ~ display;  or implies what is apparent, as opposed to what is within or is spiritual or mental: an ~ show of courage belied his inward terror.   （后缀ward表示direction方向，如forward/backward/upward/downward/afterward/inward/southward向南/homeward向家/sunward向阳）  用途很广，如outward display/calm/appearance/symptoms/movement/flight外在表露/镇定/外表/症状/向外运动/向外飞行


outside: usually implies a position on or a reference to the outer parts or surface of a thing: a shutter covered the ~ of the window; it also tends to apply to what is beyond some implied limit: looked for caused in ~ influences.      义项1又如outside wall/corner/door外墙/角/门，the outside edge of the foot脚的外沿  义项2又如sitting outside the door站在门外，the outside world外面的世界，it is raining outside外面在下雨，activities outside the law非法活动，如an outsider局外人，指不属于某群体或不被接纳的人，如she felt like an outsider in her new school她在新学校感觉自己像个局外人


external: close to outside in meaning, may be preferred when location beyond or away from the thing under consideration is implied: directed their attention to ~ affairs.    又如external influence/pressure外部影响力/压力/外在现实/外交事务，the medication is for external use only该药只能外用，反义词组for internal use only仅供内服，或仅供内部使用，都比较常用


exterior: also close to outside, may be preferred when location on the surface or outer limits of the thing is implied: gave the ~ of the building a fresh coat of paint.


outer外部: 保留了out比较级含义，表示更靠外，离"inner内部"物体或中心更远，outward向外外表: 指动作的方向向外，还表示外表的而非内心的，outside外部: 表示某物的靠外部分，或某范围以外 ，external外部: 同outside义项2，常表示当前考虑事物以外，exterior外部: 同outside义项1

记忆方法: 1）首字母OOOEE，out,ex都是表示外的词根<==外部        "外"是"内、里"的反义词，构形含义尚不明确，最早和"卜"是同一个字，因此应和占卜有关  本义是1、方位词，不在某一界限以内的，如外表里应外合课外此外   2、距离关系远的生疏的，如外国外地外戚外甥见外外行   3、附加的，如另外外号外快外传

         2) 练习一下

         3）外部的意思是位于之外mean being or placed without something.首字母OOOEE，out,ex都是表示外的词根<==外部     这里without不是表示没有而是within的反义词: 在...以外