Common Mistake: PIN number / ISBN number

One of the most common mistakes people make when using acronyms is adding the word "number" after the acronym itself. A prime example of this is the phrases "PIN number" and "ISBN number."

What is a PIN number and an ISBN number?

A PIN (Personal Identification Number) is a numeric password used to access various digital services, like banking or mobile phones. An ISBN (International Standard Book Number) is a unique numeric identifier used to distinguish published books.

Although both PIN and ISBN already include the word "number" in their acronyms, it is commonly seen and heard with the redundant word added, which results in "PIN number" and "ISBN number."

Why is the phrase redundant?

The letters "N" in both PIN and ISBN actually stand for "number." Therefore, when we say "PIN number" or "ISBN number," we are essentially saying "Personal Identification Number number" or "International Standard Book Number number."

This redundant usage can happen because we may feel that the acronym alone is not clear enough, so we add the word "number" instinctively. However, doing so is incorrect and unnecessary.

The Correct Usage

In order to use these acronyms correctly, we should omit the word "number" when using PIN or ISBN. For instance:

• Incorrect: Please enter your PIN number to access your account.
• Correct: Please enter your PIN to access your account.
• Incorrect: The ISBN number of this book is 978-3-16-148410-0.
• Correct: The ISBN of this book is 978-3-16-148410-0.

By removing the redundant word "number," we have simplified the sentences and made them grammatically correct.

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