primer
noun- [uncountable, countable]
a type of paint that is put on wood, metal, etc. before it is painted to help the paint to stay on the surface 底漆；底层涂料 - [countable] (North American English)
a book that contains basic instructions 初级读本；入门书 - [countable] (old-fashioned)
a book for teaching children how to read, or containing basic facts about a school subject 识字课本；启蒙读本
Word Originsenses 2 to 3 late Middle English: from medieval Latin primarius (liber) ‘primary (book)’ and primarium (manuale) ‘primary (manual)’.