y chance 碰巧 偶然 一般接在句子后面
例句：I heard their talking by chance.
我偶然听到他们的谈话.
I met her quite by chance.
我遇见她完全是偶然的.
I won purely by chance.
我完全是侥幸打赢的.
come across v.偶遇；无意中发现；讲得清楚明白；[口]给人…印象
偶然遇见 | (越过…而)来到 | 偶然碰见 | (无意中)碰到,找到,想到
例句：Perhaps I shall come across him in France.
也许我会在法国遇见他.
I came across this book in an old bookstore in London.
我在伦敦一家旧书店里发现了这本书.
Your speech didn't come across; nobody understood your opinion.
你的演说讲得不明不白,没有人能听懂你的意思