If you happen to be invited to a party at the United States Embassy in Ulan Bator, Mongolia, you might address your R.S.V.P. to “eyebrows.conforms.zebra.” Have a care package for a student at the Institute of Finance and Economics of Mongolia? Writing “during.snapper.housework” on the parcel will get it there.

These oddly poetic three-word codes will soon act as a stand-in for the more common addressing convention of house number, street name and postal code, which never quite caught on in Mongolia, one of the world’s most sparsely populated countries.

They are the invention of a British start-up, What3Words, that has mapped the world into 57 trillion patches of nine square meters and given each one a unique three-word identity.

“Words are easier to remember and communicate than GPS or other alphanumeric systems,” said Giles Rhys Jones, a What3Words spokesman.