What does the word 'conservation' mean when it comes to physics?

NumberOfTails_i- the initial number of tails
NumberOfTails_f- the final number of tails
The conservation of tails can be written by saying that the initial and final number of tails are equal, or that the change in the number of tails is zero

1. Today is the initial state
1. Tomorrow is the final state
1. ∆ means final minus initial
1. Even if you don't know what momentum is, you can still apply ∆ to it
1. p_i with an arrow- the initial momentum vector
2. p_f with an arrow- the final momentum vector
3. If initial and final momenta are equal, then ∆p is zero
1. Even if you don't know what energy is, you can still apply ∆ to it
1. E_i- the initial energy
2. E_f- the final energy
3. Energy conservation means that initial and final energies are equal, or that ∆E is zero

Here you'll see one common trick for using the ∆ symbol in conservation problems.