Define one Curie.

Hint:Curie is basically used to measure the amount of radioactivity. This quantity is named in honour of French physicist Pierre Curie and his wife Madam Curie. Curie is described as a certain quantity of radioactive decays per second that quantity is equal to decay of 1 gram of radium per second.

Complete step by step answer:
Radioactivity basically refers to the particles which are emitted from nuclei as a result of nuclear instability. The unit for measuring the amount of radioactivity was the curie \[\left( {Ci} \right)\]. Initially, correspond to one gram of \[radium - 226\]. Recently defined as \[1{\text{ }}curie{\text{ }} = {\text{ }}3.7 \times {10^{10}}\] radioactive decays per second.
And which is roughly the amount of decays that occur in 1 gram of radium per second and is \[{\text{ }}3.7 \times {10^{10}}\] becquerels \[\left( {Bq} \right)\].
The typical human body contains roughly \[0.1{\text{ }}\mu Ci{\text{ }}\left( {14{\text{ }}mg} \right)\] of naturally occurring \[potassium - 40\]. A human body containing \[16{\text{ }}kg\] of carbon would also have about \[24\] nanograms or \[0.1{\text{ }}\mu Ci\] of \[carbon - 14\]. Together, these would result in a total of approximately \[0.2{\text{ }}\mu Ci\] or \[7400\] decays per second inside the person's body (mostly from beta decay but some from gamma decay).

Note:
Power:
The power emitted in radioactive decay corresponding to one curie can be calculated by multiplying the decay energy by approximately \[5.93{\text{ }}mW/MeV.\]
SI units:
The SI unit of radioactivity is becquerel \[\left( {Bq} \right)\] and this term has been kept after Henri Becquerel. It is defined as: The activity of a quantity of radioactive material where one decay takes place per second.
Some measuring quantities:
\[1{\text{ }}curie{\text{ }} = {\text{ }}3.7 \times {10^{10}}\] radioactive decays per second
1 becquerel = 1 radioactive decay per second \[ = {\text{ }}2.703 \times {10^{ - 11}}{\text{ }}Ci.\]
\[1{\text{ }}rutherford{\text{ }} = {\text{ }}1.106\] radionuclide decays per second