subject

issue, subject, theme, topic

这些名词均有“主题、话题”之意。
issue: 指有争论、议论，急需讨论研究的热点话题。
subject: 一般用词，使用广泛。指书籍、文章、演讲、讨论等所隐含的、暗示的，需要由读者或听众推断的主题或中心话题。
theme: 系正式用词，多指文学、艺术作品的主题，或论文、演说的主题。
topic: 普通用词，含义广泛，但其范畴小于subject。既可指文章、讲话的题目，谈话的内容，又可指提纲中的标题甚至段落的主题或中心思想。

liable, apt, likely, prone, subject

这些形容词均含“倾向于……的、易于……的”之意。
liable: 指易于产生某种不利的结果，侧重偶然性，常表示警告或提醒。
apt: 口语中常用，指自然的或习惯的倾向，无特殊的褒贬意味，常指在一般情况下发生的事。
likely: 侧重可能性，用于指将来，预言希望或所不希望的结果。
prone: 多用于人，着重其本性，或倾向于某种错误、弱点或不良行为等。
subject: 指确实可以察觉的倾向，也就是总结出来的规律。

名词 subject:

1. the subject matter of a conversation or discussion
   同义词：topic, theme
2. some situation or event that is thought about
   同义词：topic, issue, matter
3. a branch of knowledge
   同义词：discipline, subject area, subject field, field, field of study, study, bailiwick, branch of knowledge
4. something (a person or object or scene) selected by an artist or photographer for graphic representation
   同义词：content, depicted object
5. a person who is subjected to experimental or other observational procedures; someone who is an object of investigation
   同义词：case, guinea pig
6. a person who owes allegiance to that nation
   同义词：national
7. (grammar) one of the two main constituents of a sentence; the grammatical constituent about which something is predicated
8. (logic) the first term of a proposition

动词 subject:

1. cause to experience or suffer or make liable or vulnerable to
2. make accountable for
3. make subservient; force to submit or subdue
   同义词：subjugate
4. refer for judgment or consideration
   同义词：submit

形容词 subject:

1. not exempt from tax
2. possibly accepting or permitting
   同义词：capable, open
3. being under the power or sovereignty of another or others
   同义词：dependent
4. likely to be affected by something (especially something unpleasant)

1. I am French by birth and a British subject by marriage.
   我按出生是法国人，因结婚而成为英国公民。
2. How many subjects are you studying this semester?
   这学期你选了几门课程？