印子
trace; impression (e.g. footprint); abbr. of 印子錢|印子钱[yin4 zi5 qian2], usury
因子
factor; (genetic) trait; (math.) factor; divisor
引子
introduction; primer; opening words
印子钱
usury; high interest loan (in former times)
注音字母
see 注音符號|注音符号[Zhu4 yin1 Fu2 hao4]