底子

dǐzi
  1. base
  2. foundation
  3. bottom

CEDICT

Entry Composition

1 底 dǐ
  1. bottom; base
  2. background; foundation
  3. copy (of a manuscript or receipt etc) kept as a record
  4. (suffix) end of a year or month
  5. (math.) radix; base (abbr. for 底数 dǐshù)
2 子 zi noun suffix, as in 椅子 yǐzi "chair"