Advertising is a dog-eat-dog business.

KEY & NOTES:

广告业是一个竞争残酷的行业。

在汉语也有“狗咬狗”的习语，意思跟英文中的“dog-eat-dog / dog eat dog”
有点相似，都有比喻“自相残杀”的含义，但是，由于文化背景的影响，
中西方对狗的情感有所不同，所以中文里的“狗咬狗”就含有鄙视的意思；而这里的
“DOG-EAT-DOG”只说明了“自相残杀的，竞争激烈或残酷的”含义。我们来看看两个
例句吧：
In showbusiness it's dog eat dog - one day you're a star, the next
you've been replaced by younger talent.

It's a dog-eat-dog world out there so you've got to know who your
real friends are.