| 先天 | xiān tiān | embryonic period (contrasted with 後天|后天 [hou4 tian1]) / inborn / innate / natural |
| 后天 | hòu tiān | the day after tomorrow / life after birth (the period in which one develops through experiences, contrasted with 先天[xian1 tian1]) / acquired (not innate or congenital) / a posteriori |