Topic 1: Basic Nuclear Physics – Step 18

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English Idioms

What does “double-edged sword” mean?

In Chapter 4, radioactivity is described as a “double-edged sword.”

This expression comes from Arabic and is a metaphor meaning something has or can have both positive and negative parts or consequences. Taken from the idea that two sides of the same sword blade are sharp.


“Freedom of expression … can be a double-edged sword.”

Linda Connors

“A shaft of sunlight is a double-edged sword. The sun powers life on earth, but its ultraviolet radiation capable of bending DNA, RNA, and protein molecules into harmful shapes-poses a threat to life.”

 Jay Withgott, “Feeling the burn,” Natural History, Vol. 110, No. 6; p. 38, 2001 (Jul/Aug)

Think Ahead: How is radioactivity a “double-edged sword”?