one billionth

/wʌn ˈbɪljənθ/
noun
  1. One part out of one billion equal parts of something; 1/1,000,000,000.
    • The scientist measured a one-billionth of a gram of the substance.
    • A nanosecond is one-billionth of a second.
    • Only one-billionth of the water in the ocean is drinkable without treatment.
Synonyms
adjective
  1. Being the last in a series of one billion items; occupying the position after 999,999,999.
    • She was the one-billionth visitor to the website and won a prize.
    • The one-billionth grain of sand marked the end of the count.
    • The company celebrated selling its one-billionth product.