summation, plus, improver, accession, increase, gain, adding, additional, complement, besides, more...

subtraction, removal, deduction, decrease, elimination

subtraction, multiplication, division, exponentiation, modulus, increment, decrement, bitwise OR, more...

valuable, new, important, late, welcome, recent, further, simple, useful, small, net

include add,   building extension,   extension of,   an extension of,   list of corrections,   math operation,   calculation of sum,   new part,   counting in,   being added,   house add-on