名人教英文：infinitive何时不跟to？（1）
英语文法有所谓subject-verb agreement，即动词的单复数状态要配合主语的人称，例如john works hard every day的主语是第三人称的john，所以动词work须加s。
然而，mrs chan makes her son work hard every day不能写成mrs chan makes her son works hard every day——因为her son不是句中主语，work也不是句中主要动词。这个句子的结构如下：（详见附表）
不定式（infinitive）可分为to-infinitive和bare infinitive两种。我们经常用到「动词 (verb) + 宾语 (object) + to-infinitive」的句式，to-infinitive由to和动词的最基本形态组成，如：
‧he asked me to close the door.
‧the teacher told the students to submit their assignments (作业) by friday.
不过，有些动词配bare infinitive，即是不带to的不定式。常见的例子有let、help、make和have，这几个动词属于causative verbs（使役动词），用以表示「让/使某事情发生」。let、make和have必须配bare infinitive，不可加to，而help则可配to-infinitive或bare infinitive。例如：
‧the security guard did not let the suspicious-looking (形迹可疑的) man enter the building.
‧the measures announced in the policy address may help middle-class families (to) realise their dreams of home ownership.
‧john's mother makes him tidy up his room every weekend.
‧i'll have a florist send you a fruit basket.
make someone do something有迫令人做某件事情的意思。have someone do something则指叫别人完成某事，但没有强迫之意，可以是要求、安排或说服，但总而言之并非自己亲自去做，这就是i will have someone do something和i will do something的分别。
至于get someone to do something的意思和have someone do something相似，但必须配to-infinitive。
另外还有一类动词通常配bare infinitive，下周继续介绍。
英语单词词汇学习：
assignments……作业
suspicious-looking……形迹可疑