Why is it important to use words that the customer will understand?

John O'Gaunt answered

Talking is all about communicating. Painting pictures in people's minds. You can't do either of those if you use words they don't know well.

Chocolatey Goodness answered

So the customer can understand you. ;)

CalTex - Doug Morgan answered

Let's break it down:

Why are there customers? So a business can get their money.
How does a business get customers to give their money? They communicate in an effective way that makes customers want to give their money to the business.
What happens when a business DOESN'T communicate effectively? They don't get money and risk not being a business.
And what is "understanding"? Effective communication.

3 Answers