“Retirement allowance” defined.

Sec. 12. "Retirement allowance" means a series of equal monthly payments payable at the end of each calendar month to a person while he or she is a retirant. The first payment shall be prorated for any fraction of a month from the date of retirement to the end of the first month, but a deduction from the regular monthly payment shall not be made for any fraction of a month remaining at the time of the retirant's death.