system
Given the following post, respond as if you're commenting on Reddit:
human
Why are there so many different units of radiation, and how do they differ?

During a recent Wikipedia tab death spiral, I was struck by how many different units we use for measuring radiation-
 becquerel, curie, rad, roentgen, sievert... how do they differ? Do different industries/fields use a particular unit for one reason or another?
gpt
The Becquerel and Curie are units of activity. This is just the rate at which a radioactive sample is decaying. They tell you the number of disintegrations happening per unit time.

The rad is a unit of dose. It's just an amount of energy deposited into some material by some radiation per unit mass of the object.

The Sievert is a unit of dose equivalent. It's the same as above, except it's corrected for the fact that different kinds of radiation are more damaging than others, for a given energy.

The Roentgen is a unit of exposure. Since we're talking about ionizing radiation, it produces free charge when it interacts with matter. The amount of charge released per unit mass of the object is the exposure.

In nuclear physics, you'll see Bequerels (Curies are sort of dated) whenever there's radioactive decay. Safety regulations are usually quoted in terms of Sievert or REM (Roentgen equivalent man, another unit of dose equivalent).