doubtless

1 of 2

adverb

doubt·​less ˈdau̇t-ləs 

1

: without doubt

2

: probably

doubtless

2 of 2

adjective

: free from doubt : certain

doubtlessly adverb

doubtlessness noun

Synonyms of doubtless

Adverb

• certainly
• surely
• definitely
• sure
• probably
• clearly
• undoubtedly
• likely

Adjective

• sure
• confident
• assured
• certain
• positive

Examples of doubtless in a Sentence

Adverb

she is doubtless the one and only girl for me

doubtless you have heard this story before, but I'll tell it anyway

Adjective

another one of his doubtless predictions that will never come true

Recent Examples on the Web

Adverb

The scrub was doubtless disappointing for many space fans, including Minaj, who was on hand at Starbase for today's launch attempt. —Mike Wall, Space.com, 22 May 2026

Brother Lawrence Washington’s military service doubtless turned George’s British empires eyes in that direction, yet the temporary nature of Lawrence’s service gave George little more than a taste of what a life at arms entailed. —Literary Hub, 20 May 2026

Adjective

As a result, mathematical truths do not make up a unified whole of equally indubitable truths; instead, their status as knowledge varies gradually from doubtless facts to increasingly uncertain hypotheses. —Quanta Magazine, 18 May 2026

Lastly, while there is doubtless a tradeoff between construction costs and operations, a smooth operation at the big airport this coming summer — the busiest travel season — sure as heck needs to be a priority. —The Editorial Board, Chicago Tribune, 4 Mar. 2026

Word History

First Known Use

Adverb

14th century, in the meaning defined at sense 1

Adjective

15th century, in the meaning defined above

Kids Definition

doubtless

1 of 2 adverb

doubt·​less ˈdau̇t-ləs 

1

: certainly

2

: probably

doubtless

2 of 2 adjective

: free from doubt : certain

doubtlessly adverb