Real Dictionary

introduction
If you refer to a book as an introduction to a particular subject, you mean that it explains the basic facts about that subject.
countable noun: The introduction to a book or talk is the part that comes at the beginning and tells you what the rest of the book or talk is about.
countable noun: You can refer to a new product as an introduction when it becomes available in a place for the first time.

introduction in American English
an introducing or being introduced
noun: the act of introducing or the state of being introduced