Why is the ninth month called September?
cumulative cu·mu·la·tive (kyōōm'yə-lā'tĭv, -yə-lə-tĭv)
Increasing or enlarging by successive addition.
Acquired by or resulting from accumulation.
Of or relating to the sum of the frequencies of experimentally determined values of a random variable that are less than or equal to a specified value.
Of or relating to experimental error that increases in magnitude with each successive measurement.