Crossword clues for the word: HALFLIFE The word HALFLIFE has appeared as an answer to at least 9 crossword clues on different crossword puzzles. Crossword clues for HALFLIFE Showing 1 to 9 of 9 results Clue(s) *Physics period "About 5700 years, for carbon-14" "Decay concept, in physics" 24,110 years, for plutonium 239 Carbon 14 feature Feature of radioactive materials Radioactive decay measure Radioactivity figure Semi-existence leads to period of decay