1 the act or an instance of introducing; the process of being introduced.
2 a formal presentation of one person to another.
3 an explanatory section at the beginning of a book etc.
4 a preliminary section in a piece of music, often thematically different from the main section.
5 an introductory treatise on a subject.
6 a thing introduced.
Etymology: ME f. OF introduction or L introductio (as INTRODUCE)
Useful english dictionary. 2012.