“A diamond is forever” means the strength and resilience of a diamond. In other words, it means that a diamond lasts forever on account of its strength and resilience. However, now it is used for marriages where diamond rings are exchanged.
The origin of “a diamond is forever” lies in this marketing tagline coined by a copy writer Frances Gerrity at a marketing agency in Philadelphia in 1947. Dee Beers, a brand, used this tagline to boost its sale of the diamonds following the Great Depression. It is stated that since that day, De Beers has used this tagline to increase sales of its diamonds.
Example in Sentences
Example #1: The salesgirl makes fun of his purchase of a common ring saying no matter what you do, a diamond is forever.
Example #2: A woman is more pleased with a diamond ring than with a Ferrari, for a diamond is forever.
Example #3: When she said that a diamond is forever, I could not understand that she wants to purchase a diamond ring or a diamond bracelet.