What are prefixes?

source: JamesESL English Lessons     2013年8月29日
http://www.engvid.com/ Do you know what a prefix is or a morpheme is? In this English class, you will be introduced to six basic prefixes: ad-, syn-, sub-, ob-, in-, and com-. You will learn what they mean and how they change words. Take a quiz on this lesson here: http://www.engvid.com/learn-english-p...