等差級數

等差 dengˇ chaˉ

(Equal) Equal difference, Equal steps

級 jiˊ

Grade, Rank, Level, Class, Step, Stage, Decapitated Head

數 shuˋ shuˇ shuoˋ

Count, Math, Number of, Amount, Several, (Shu3), Name, Numbers, Enumerate, (Shuo4), Frequent, Often, Over And Over