半はん減げん期き

noun

half-life

Technical term in physics and chemistry for the time required for a quantity to reduce to half its initial value, most commonly used for radioactive decay.

• ウラン238の半はん減げん期きは約やく45億お年くねんです。

  The half-life of uranium-238 is about 4.5 billion years.

• この薬くすりの血けっ中ちゅう半はん減げん期きは短みじかい。