用英语说一次巧合怎么说

To say "a coincidence" in Engpsh, you can say "a coincidence" or "a happy coincidence." Here are some example sentences:

"It was just a coincidence that we ran into each other at the mall."
"It was a happy coincidence that I was able to find a parking spot right in front of the store."

You can also use the phrase "by coincidence" to describe how something happened by chance:

"I found out about the concert by coincidence when I saw the flyer on the bulletin board at the coffee shop."
"We met by coincidence on the subway and ended up sitting next to each other for the entire ride."