II.in [美 ɪn, 英 ɪn]副in often appears as the second element of certain verb structures in English (close in, hand in, stand in, etc). For translations, see the relevant verb entry (close, hand, stand, etc).
His research work has centred on several aspects of pregnancy, including maternal recognition of pregnancy, in vitro fertilization and the immunology of pregnancy in animals and humans.
In vitro fertilization makes breeding cheetahs easier because researchers do not have to transport cheetahs from the wild to breed with the cheetahs in captive-breeding programs.