The phrase ‘word of mouth’ refers to verbal communication. This phrase is usually used to talk about recommendations that are given from one person to another. ‘Word of mouth’ is considered a successful form of advertising as in when people recommend your product or service to a friend or family member. News and rumours can also spread by ‘word of mouth’. This is a common phrase usually used to talk about professional services.

1. The old story was never written anywhere. Instead, it was passed down by word of mouth.
2. The rumours of him cheating on his wife spread through the town by word of mouth.

1. In the early days, Claire didn't have the money to advertise her business. It grew purely by word of mouth.
2. Most of my trade comes from word-of-mouth recommendations. It shows that I have many satisfied customers.
3. Word of mouth is one of the most powerful forms of advertising. People trust their friends and family for recommendations.