This rain looks as if it has set in for the rest of the day.
看来今天雨不会停。
If you get bitten by a dog, you have to make sure the wound is cleaned well, or an infection could set in.
如果你被狗咬了,必须确保伤口彻底清理干净,否则可能会发生感染。
Despair seems to have set in among the team.
整支队伍似乎都陷入了绝望之中。