How do I know if my book is a first edition?

What is a first edition book?

A first edition is a book that has been printed and distributed for the first time. Books can go through several print cycles, sometimes with edits or additional material (e.g. new introductions, or author notes).

A book in its original form—during its initial release (or first printing) to the public—is what is generally defined as a first edition by collectors and sellers. 

How do I know if my book is a first edition?

Different publishers use different identifiers. The general rule of thumb is to take a look at the copyright page and look at the numbers and dates.

The number line:

A number line is usually present (that's the line of numbers on the copyright page). Usually, if a one is present in the line then it's a first edition. For example, 9 8 7 6 5 4 3 2 1 and 1 3 5 7 9 10 8 6 4 2 are both examples of first editions.

Edition Identifiers:

A first edition does not always equal first printing. Some publishers use the words 'First Edition' or 'First Printing' on their copyright page, but it's still worth checking the number line in this case. Some publishers leave the words ‘first edition’ on the copyright, even when the book is in its third print run. For example:

First edition
3 4 5 6 7 8 9 10
(Third printing)

Dates:

If the date on a copyright page matches the date on the title page, it's likely that your copy is a first edition. These dates can differ if the publication date is earlier than copyright is acquired, but if this is the indicator used you will want to ensure both dates match.