Usage of 'Textbook' for a book which helps students to understand their lessons?

[Morteza]

Hi everybody,
Can we use "Textbook" for a book which helps students to understand their lessons and do their exercises for them Or we must use other expressions like educational-aid or something like that?!
Many thanks,
Morteza

[Kitosdad]

Good morning Morteza. Thanks to Google ;

A textbook is a manual of instruction or a standard book in any branch of study. They are produced according to the demand of educational institutions. Although most textbooks are only published in printed format, many are now available as on-line electronic books and increasingly in scanned format in P2P networks.

Kitos.
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[Morteza]

Hi Dear Bill,
Thanks for your kind response!
Morteza