Monoisotopic mass

When we talk about "mass," we're usually talking about how heavy something is. But when scientists talk about "mass," they're usually talking about how many tiny little particles (called atoms) something is made of.

Now, different atoms can have different numbers of something called "neutrons" in their middle. Neutrons are like little weights that help make the atom heavier.

So, when scientists talk about "monoisotopic mass," they're talking about how much an object weighed if it was made entirely of one particular kind of atom, with a very specific number of neutrons. This is really useful for scientists who want to know exactly how heavy something is, down to the teeniest, tiniest detail!