Grammar 4 min read

Indubitably Definition and How to use it in a Sentence

Main Indubitably Takeaways:

  • Indubitably is an adverb that means there is no doubt something is true, or that something is impossible to doubt.
  • It’s similar to undoubtedly and doubtless, but is much more certain.
  • It’s best for formal or academic settings. It can seem pretentious.
  • If you want the adjective version, use indubitable.
  • It is an old-fashioned word with Latin origins and has been around since the 15th century

If you’re 100% convinced that something is true, indubitably is an elegant way to say there’s no doubt in your mind.

The pink square character INK Mascot wears a top have, monocle, pronounced mustache, and three-piece suit. He holds a glass of brandy and is pictured next to the word INDUBITABLY.
Indubitably means you’re 100 percent sure about something or that you believe it’s real or accurate without a doubt.

What Does Indubitably Mean?

Indubitably means that something is impossible to doubt or unquestionable. It indicates a stronger degree of certainty versus similar words like undoubtedly. Basically, it’s a very formal way to say “no doubt.” This adverb comes from the Latin word dubitabilis, which means doubtful. Combined with the prefix -in, it means without a doubt. Only use this word when you are convinced that something is 100% true. It can be used as a response to question.

How Do You use the Word Indubitably in a Sentence?

Indubitably Sentence Examples:

After her boyfriend cheated, Sheila wasn’tindubitablyconvinced of his love for her.
The judgeindubitablybelieved Rex was an excellent parent, so Rex received primary custody.
Sami argued that Joey’s doctorate degree made himindubitablyoverqualified for a janitorial position.

Chris: You will join us for the Opera next month, won’t you?

Don: Indubitably!

Pronunciation Guide:

  • in-DOO-bit-a-blee.
  • Make sure you emphasize the ‘du,’ pronounced doo. It rhymes with boo or who.

When to use Indubitably

Because this isn’t a popular word, it’s best for professional conversations. Use it while speaking with your boss or meeting with a client. The word also works in academic settings.

Indubitably is not used often in everyday conversations. Instead, phrases like without a doubt are more common.

What’s more, it may seem pretentious or even sarcastic to use this very refined word in casual texts or emails.

In these informal situations, try something like certainly, unquestionable, or doubtless.

A boy holding a placard that reads "indubitable." Synonyms of indubitable are pictured to the right of him that include: unquestionable, indisputable, unarguable, undoubtable.
When you need the adjective form, use indubitable.

What is a Synonym for Indubitably?

Formal Synonyms for Indubitably:

  • Absolutely
  • Certainly
  • Inarguably
  • Indisputably
  • Irrefutably
  • Positively
  • Undoubtedly
  • Unquestionably
  • Veritably

Informal Synonyms for Indubitably:

  • For sure
  • No doubt
  • One hundred percent true
  • Without a doubt

What is the Difference Between Undoubtedly and Indubitably?

Undoubtedly is a synonym for indubitably, which means they hold the same meaning. Undoubtedly was derived from the French word douter in the mid-1400s. It means to be afraid or doubtful. Early users of the word then added the prefix un to describe the opposite of doubter, forming the term we now know as undoubtedly (without a doubt, plain truth). In essence, you can use undoubtedly in place of indubitably, or vice versa. However, indubitably is rarely used in conversational communication since it carries the connotation of a formal term.

The teacher indubitably believed what the student said.
The teacherundoubtedlybelieved what the student said.
The manager was indubitably impressed by Jane’s experience and credentials.
The manager was undoubtedly impressed by Jane’s experience and credentials.

Why Doubtless and Undoubtedly Aren’t Perfect Synonyms

The difference is that the first two leave some room for doubt while indubitably leaves zero room for doubt.

Indubitably works well if you’re completely convinced something is valid or accurate. If you have doubts, you may use a different word, such aslikely or probably.

For example, doubtless literally means without a doubt. But, in practice, you typically see this word used as a synonym for probably.

Conversely, undoubtedly also means without a doubt. Unlike doubtless, this adverb is stronger than probably. However, it’s still not as strong as indubitably.

An infographic outlining this information: Indubitably is a formal way to say that something is impossible to doubt. A curly-haired man telling his friend "there's no doubt that you'll win!" Informal synonyms for indubitably are one hundred percent sure, without a doubt, no doubt, and for sure. Formal synonyms for indubitably include absolutely, certainly, inarguably, indisputably, irrefutably, and positively. Remember, only use the word indubitably if you are 100% sure that something is true.
INK Indubitably Infographic

These Words are Similarbut are not 100% True:

  • Doubtlessly
  • Undoubtedly
  • Certainly
  • Unquestionably

None of these words is as strong as indubitably, though. Only choose indubitably if you need a word indicating you’re 100% convinced something is true.

Other Forms of Indubitably

indubitable:(adjective) undisputable; without a doubt

Many people argue there areindubitablebenefits of wearing a face mask during a pandemic.
“It’s anindubitablefact that vaccines work,” the scientist told the president.
“I have anindubitablebelief that I will love you for as long as I am alive,” Maritza told her son.

Words Similar to Indubitable

  • Evidently
  • Likely
  • Probable
  • Irrefutable
  • Indisputable
  • Inarguable
  • Undeniable
  • Undebatable

Are you Comfortable Using This Word? Test Your Skills With This Quick Quiz…

Indubitable Question #1

Indubitable is a real word that means doubtful.
Correct! Wrong!

The answer is FALSE. Indubitable means without a doubt, impossible to doubt, or unquestionable.

Indubitably Question #2

What part of speech is indubitably?
Correct! Wrong!

The answer is D. Indubitably indicates the degree of certainty.

Indubitable Definition Question #3

Which word is NOT a synonym for indubitable?
Correct! Wrong!

The answer is B. Indubitable means impossible to doubt. Other synonyms for this word include indisputable, incontestable, undeniable, and certain.

Indubitably Question #4

It's appropriate to use indubitably in casual conversations with friends.
Correct! Wrong!

The answer is FALSE. Indubitably is best for formal communication such as academic writing and work email.

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Pam Weber

Pam is an expert grammarian with years of experience teaching English, Writing and ESL Grammar courses at the university level. She is enamored with all things language and fascinated with how we use words to shape our world.

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