R.L. Trask 
Language: The Basics [PDF ebook] 

What makes human language unique?
Do women speak differently from men?
Just what is the meaning of 'meaning’?
Language: The Basics provides a concise introduction to the study of language. Written in an engaging and entertaining style, it encourages the reader to think about the way language works.
It features:

* chapters on ”Language in Use”, ”Attitudes to Language”, ”Children and Language” and ”Language, Mind and Brain”
* a section on sign language
* a glossary of key terms
* handy annotated guides to further reading.
Providing an accessible overview of a fascinating subject, this is an essential book for all students and anyone who”s ever been accused of splitting an infinitive.