The document defines several key mathematical concepts: - Additive identity is the value of 0, as adding 0 to any number yields the original number. - Multiplicative identity is the value of 1, as multiplying any number by 1 yields the original number. - An additive inverse of a number x is -x, as x + (-x) = 0. - A multiplicative inverse or reciprocal of a number x is 1/x. - Decimals represent fractions in base-10, with the 10th, 100th, 1000th parts called tenths, hundredths, thousandths and so on.