tautology

A tautology is the unnecessary repetition of an idea, statement, or word whose meaning has already been expressed, as in 8 a.m. in the morning. (The label a.m. indicates the morning, so in the morning creates a tautology).

Tautologies say the same thing twice without adding new information or emphasis.

In logic, tautology has a more specific meaning: a statement that is always true, as in Statement 1 is true or not true or Either we will arrive on time or we will not arrive on time.  

Example: My professor pointed out that the phrase “evening sunset” is a tautology because sunsets always happen in the evening.

The first records of the word tautology come from the 1500s. It comes from the Greek tautología. The combining form tauto- means “same,” and the ending -logy can be used in reference to writing or discourse.

Tautologies are often avoided in writing because they consist of an unnecessary repetition of the same information without adding any emphasis. Of course, this is sometimes a matter of preference. The phrases dilapidated ruins and dry desert can be considered tautologies because the adjective in each expresses something already expressed by the noun. But it could be argued that they add emphasis. Some tautologies are more obvious, as in She’s a beginner who just started or We are currently closed at this time. 

In logic, tautology refers to a statement that’s true in every interpretation, as in Either we will win or we will not win. 

The word redundancy is similar, but it’s usually used more generally, often for the simple repetition of a specific word, as in The Department of Redundancy Department or $20 dollars (in which dollars is unnecessary due to the use of the symbol $). By contrast, an oxymoron is a phrase or expression that uses terms that contradict each other, as in the phrase growing smaller.

What are some other forms related to tautology?

• tautological (adjective)
• tautologic (adjective)
• tautologous (adjective)
• tautologism (noun)
• tautologize (verb)
• tautologically (adverb)
• tautologously (adverb)
• nontautological (adjective)

What are some words that share a root or word element with tautology? 

• tautonym

What are some words that often get used in discussing tautology?

• repeat
• needless
• unnecessary
• redundant
• logic
• recurrence
• reiteration

The word tautology is often discussed in the context of writing as something to avoid. When spotted in real life, tautologies are often humorous.

'currently unable to offer this service at this time' is a bit of a tautology innit. (MBNA telephone helpline if you're interested.)

— Jack Fraser (@muninnherself) March 30, 2020

“Face mask” is a tautology. Discuss.

— Tim Parker (@pozlit) April 18, 2020

Love never fades.

No such thing as "true love". That's tautology. If it's not true, it's not love. Period. https://t.co/QxGNHEIxcT

— 🇳🇬Dr. Strange🇦🇺 (@the_ngozi) April 13, 2020

Which of the following phrases is an example of a tautology? 

A. brown dog
B. roasted carrot
C. frozen ice
D. shiny car