Word-of-mouth クチコミ

・Our business has grown through word of mouth.
（我々のビジネスは口コミで広がっています）

・I found out about it by word of mouth.
（口コミで知りました）

・This product became popular through word of mouth.
（この商品は口コミで人気がでました）

https://hapaeikaiwa.com/2013/07/31/%25e2%2598%2586%25e3%2582%25a4%25e3%2583%2587%25e3%2582%25a3%25e3%2582%25aa%25e3%2583%25a0%25e2%2598%2586%25e3%2580%258cword-of-mouth%25e3%2580%258d%25e3%2581%25ae%25e6%2584%258f%25e5%2591%25b3%25e3%2581%25a8%25e4%25bd%25bf%25e3%2581%2584%25e6%2596%25b9/