gastigi

-Ig- means to cause, and here it causes guesthood. Gasto is a guest; gastigi is to make somebody a guest, which in practice means to take them in, feed them and give them a bed. English needs a whole different word, host, and then has to explain that it is unrelated to the hostility in hostile. Esperanto derives the verb from the noun and is done. The igi and iĝi article is the general case: -ig- does something to somebody else, -iĝ- has it happen to you, and gastiĝi would be to become a guest, which is what the visitor does while the household gastigas.

The family is unusually complete. Gastejo is the guest place, an inn or a hostel; gastama is hospitable, literally guest-loving; gastamo is hospitality; gastiganto is the host and gastaro the assembled guests. Every one of them is built from the same four letters, and you can generate the lot without looking anything up.

This is not a neutral word in this language. Pasporta Servo is an Esperanto institution: a list of speakers around the world who will put up another speaker for a night or two, free, on the strength of the shared language alone. It has been running since 1974 and it is the thing many people mean when they say the movement is more than a hobby. Gastigi is what those hosts do, and the verb carries the whole idea in six letters.