back 作为副词或形容词时，强调所修饰物的位置以及动作运动方向。
back ward可用于人或物，指向后的，落后的或迟钝的。
hind 指成对并且分前后的东西的“后面的”。
behind 指一物同它物相对的位置或场所。
参考例句
1. What time is the same spelling backward and forward? 什么时候是相同的拼写向后和向前的？
2. He was standing front, facing backward, so all of us could see his face. 他是站在前面，面对着后面的，所以大家都可以看到他的脸。
3. To complete this maneuver fly, backward to a hover above the landing area. 后退飞行至降落区的上空保持倒飞停悬，即完成此动作。
英英解释
adj.
1. directed or facing toward the back or rear
2. (used of temperament or behavior) marked by a retiring nature
3. retarded in intellectual development adv.
1. at or to or toward the back or rear
2. in a manner or order or direction the reverse of normal
3. in or to or toward a past time
