动词不定式是学习英语的难点之一，也是构成长句的一个重要因素。不定式有自己的宾语、状语和补足语，组成不定式短语。在分析句子时要把不定式短语看作一个整体。不定式在句中可作主语、表语、宾语、定语、状语和补足语。
不定式短语在句中分析与翻译的实例
75.You will remember that the materials which combine to make a mixture do not completely lose their individual qualities.They do not do so because their molecules are not broken up and built into new molecules with new qualities.
你们要记住，组成混合物的各种物质完全没有失去它们各自的性质。它们之所以这样，是因为它们的分子并没有分解，没有形成具有新性质的新分子。（不定式短语to make a mixture是谓语combine的结果状语。）
76.The moon's pull causes water in the oceans to be a little deeper at the point closest to the moon and also at a point farthest from themoon，on the oppositeside of the earth.
月球的引力会引起近月点处和地球另一端的远月点处海洋的海水略深一些。（cause sth.To do sb，“引起……作……”。to be alittle deeper.……作water宾语补足语。）
77. It is also a familiar fact that a force is required to slow down or stop a body which is already in motion，and that a sidewise force must be exerted on a moving body to deviate it from a straight line.
要使一个已经运动的物体慢下来或使其停止运动就需要作用力；要使该物体偏离直线运动，就需要横向作用力，这也是大家所熟悉的事实。（it是形式主语，代替that引出的两个主语从句。不定式短语to deviate.……1ine是目的状语，其中it代替the moving body.）
78.Though only l07 elements have been discovered，they combine in enough different ways to make the millions and millions of different things in the world.
虽然只发现了107种元素，但是这些元素以不同的方式化合在一起就会形成世界上无数的千差万别的东西。（不定式短语to make.……作结果状语，说明enough.）
79.Since we have already associated flow of charge or current with the existence of potential difference，it becomes of interest and importance to establish a quantitative relation between these two quantities.
因为我们已经把电荷的流动即电流与电位差的存在联系起来，因而在这两个量之间确立一种数量关系就成为重要而值得注意的问题了。（不定式短语to establish.一quantities是主语，it是形式主语。）
80.Apart from the enormous outflow of funds from the oil-consuming countries，a more basic concern is the capability of the major exporters of crude oil to achieve a continuing production target roughly doubling output every tenyears to meet the required oil demand if present trend continues.
且不谈用油国的资金大量外流，更令人担心的重要问题是：如果目前的这种趋势继续发展下去，那么主要原油出口国是否有能力每10年大致将产量翻一番以满足对石油的需求。
（a-partfrom，“除了，且不说”。of.……oil作capability的定语，不定式短语to achieve.……continue也作定语，修饰capability.这个不定式短语中包含有：现在分词短语roughly doubling.……continue.这个短语中又包含有不定式短语作目的状语to meet.……continue和if引导的条件状语，这两个状语都用来修饰doubling.）
