What is a condition subsequent?

Within the context of wills and testamentary gifts, a “condition subsequent” is where the gift is given but can be later lost if something happens. For example, if I ran my own business, I may leave the property of that business to my son on the condition that it continues to be used for that business. So he could sell the business to someone else, allowing them to run it, and collect rent on that property. However, if he converts the business to some other business, or tries to turn it into a house, the will’s condition would kick in and he would lose the property.