后面不加介词。

去国外，出国We can't afford to go abroad this summer.今年夏天我们没有足够的钱去国外。Every time I go abroad, I have to struggle with jet lag.我每次出国都要费力地倒时差。We always go abroad in the summer.我们总是在夏天去国外。He often has to go abroad for work.他经常去国外出差。