Changing a few words can make huge differences in conversion. 

For example:

Popsa

• Old phrasing: Fast Easy Photo Books
• New phrasing: Photo books in 5 minutes

Peer Medical

•  Old phrasing: Lung cancer treatment data personalised for you.
• New phrasing: "This is hope. This tool shows me other lung cancer treatments in case my current drug stops working."

It is known as language/market fit - Using the right words to explain your product or service that resonates with prospective customers.

Early startups often underappreciate language/market fit. Instead, they focus on finding product/market fit as refining language seems like "marketing", which is usually left for a later priority.

However, not prioritising language/market fit can create difficulties, such as your ads can't pay for themselves, your marketers struggle to deliver results despite their previous success with other companies. Your salespeople struggle to sell your product.

On the other hand, companies with language/market fit usually get conversion rates of 8% - 40%.