anything that takes up space
A kid friendly definition of the word energy is, the ability to do work.
Your neck
a kid friendly definition would be two or more people that disagree on something and are not getting along.
changing
competition
not exact but the mass of an atom
A kid friendly definition would be - The head of the Catholic Church.
the definition is a sun the is colder than usual and has low mass
A kid friendly definition of disease would be "a very serious sickness a person/people could catch or already have from their parents.
Mass is the amount of matter in an object.
Because that is the definition of mass.
Something that someone has to do.