本质上，理论是从现实中抽象概括出来的。
Essentially,a theory is an abstract,symbolic representation of what is conceived to be reality.
在孩子就能说话和听懂话以前的很长一段时间，他们通过面部表情和口头表达来交流。
Long before children are bable to speak or understand a language,they communicate through facial expressions and by making noises.
多亏了现代的灌溉技术，现在庄稼能在以前只能长仙人掌和灌木的地方茂盛的生长。
Thanks to modern irrigation,crops now grow abundantly inareas where once nothing but cacti and sagebrush could live.
