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Definition of billionth

billionth

/ˈbɪl.jənθ/
bil · lionth
Plural:billionths
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billionth Lexical Profile

billionth Game Scores & Validity

• adjective

1

Constituting number one billion in a sequence; 1,000,000,000th.

Example

"The company celebrated selling its billionth smartphone this morning."

2

Being one of a billion equal parts of a whole.

Example

"A nanosecond is a billionth part of a second."

• noun

1

One of a billion equal parts of something.

Example

"The atomic clock is accurate to within a few billionths of a second."

2

The person or thing in a sequence corresponding to the number one billion.

Example

"Today's newborn was officially recognized as the country's billionth citizen."

• Rhymes for billionth

• Nearby Words

billings
billion
billionaire
billionth
billow
billowy
billy

Word Origin & Etymology

Formed in English from 'billion' (borrowed from 16th-century French, combining the prefix 'bi-', meaning 'two', with '-illion' modeled on 'million') and the Old English ordinal suffix '-th'.

Cite this Entry

Wordmom. (2026). Definition of Billionth. In Wordmom Dictionary. Retrieved Nov 5, 2026, from https://wordmom.com/dictionary/billionth
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