Chemistry help?

Why the atomic mass of carbon 12.011 rather than a perfect 12?

I'm not sure if this will violate the TOU.
But I'm not asking for the answer, I kinda just wanted to discuss it.
Isn't there more than one answer?
I'm not sure, but isn't it because...

the mass number is always aperfect number and the atomic number is always in decimal form because it's more accurate?

hahah yu seem really smarttt, ! at my school we juss round it, so we say it is a perfect 12

H/W questions are no longer against TOU
and I think it's about averages of different isotopes (it was a long time ago when I took chem so dont quote me on this)

So why is the atomic mass of carbon listed as 12.011 on the periodic table? Most elements consist of two or more isotopes. Isotopes are atoms of the same element, but with different atomic masses. Carbon has three isotopes: carbon-12, carbon-13, and carbon-14. All of these isotopes of carbon have atoms that contain 6 protons in their nuclei. The difference between these isotopes is the number of neutrons in their nuclei. Carbon-12 atoms have 6 neutrons, carbon-13 atoms have 7 neutrons, and carbon-14 atoms have 8 neutrons. Any sample of carbon will contain all three isotopes. This is why the atomic mass for carbon is 12.011.

Sorry, I should have also said, because of the presence of these other isotopes, the average weight of any sample will be 12.011

damn
im havin trouble in chemistry myself
GOD its complex lol

It is 12.011 because it exists as a mixture of isotopes having different relative abundances.