The Curie is a measure of radioactivity based on the observed decay rate of approximately one gram of radium. The Curie was named in honor of Pierre and Marie Curie, pioneers in the study of radiation. One curie of radioactive material will have 37 billion atomic transformations (disintegrations) in one second.
Pico means one one-trillionth (1/1,000,000,000,000). A picoCurie (pCi) is one-trillionth of a Curie.
Nano means one-billionth (1/1,000,000,000). A nanoCurie (nCi) is one-billionth of a Curie.
Micro means on-millionth (1/1,000,000). A microCurie (µCi) is one-millionth of a Curie.
Milli means one-thousandth (1/1,000). A milliCurie (mCi) is one-thousandth of a Curie.