What Is Tautology?

Tautology is the needless repetition of a single concept.

Examples of Tautology

Look at these examples of tautology:

• At that moment in time, the stars dimmed.
(It's always a moment in time.)
• The man who used to live next door is a single bachelor.
(Bachelors are always single.)
• The vote was totally unanimous.
(The word totally doesn't add anything.)
• He left at 3 am in the morning.
(The term am means in the morning.)
• The reason is because he left during the dinner.
(The word because doesn't add anything.)
• In our assessment, we think he is alive.
(In our assessment and we think do the same job.)
• This is a new innovation.
(Innovations are always new.)

Examples of Possible Tautology

Sometimes, you have to think whether something really is a tautology. Look at these examples:

• She died of a fatal dose of heroin.
Argument For: You don't need the word fatal.
Argument Against: She might have died from a non-fatal dose, i.e., one that wouldn't kill most people.


• Present a short summary.
Argument For: Summaries are always short.
Argument Against: Er, no they're not.


• Enter your PIN number in the ATM machine.
Argument For: The N in PIN stands for Number, and the M in ATM stands for Machine.
Argument Against: Yeah, okay. But, PIN and ATM have become standalone terms these days. It's helpful to put the words number and machine to ensure everyone understands.

"Technical" Tautology

Sometimes, tautology can be difficult to spot:

• A so-called "clean" surface.
(If the quotation marks are used to show that the surface is not clean, then there is no need for the words so-called.)