Condition precedent
The things you agree to do, or must happen, before the other guy has to do what he said he'd do. Not to be confused with consideration, which is what you give him for doing it.
So: I agree to lend you my car for ten quid, but before I let you have the keys, you must give proof you have insurance. The ten pounds is consideration; the insurance certificate is a condition precedent.
It reminds me of a story from the jolly contrarian's youth. It was decades ago, in the infancy of the credit derivatives market. A partner from Stephenson Harwood (the same one that pronounced it sw-æp and not sw-ŏp) sent his mark-up of the, er, sw-æp. He had rather gone to town, in a manner indicative of only passing acquaintance with the derivatives market.
Your correspondent’s supervising partner—an excitable fellow who now runs a newsagent in Gillingham—stormed into the room whilst I was in mid-conversation with the client, a young but quick chap from Dublin.
- “I have never been so outraged”, said the partner. “I have covered his draft with unprintable words starting with “c” and “p” ...!”
Without missing a beat, the young client interjected: