pan
The derivational marker pan turns the following word into a noun that is a causative agent, meaning it causes or allows another entity to do that verb. Compare this to mu, which refers to something that itself is doing the action:
mu ikasi - "entity that learns", "learner"
pan ikasi - "entity that causes others to learn", "teacher"
It is not specified exactly what is doing the action. In the above example, it could refer to a person, an animal, or whatever else. If you want to specify what the agent is, you can put a word before it:
nin pan ikasi - "person who teaches"
conto pan ikasi - "machine that teaches"
Using je X, you can indicate what is being caused to do the action of X:
pan makan je kuku - "bird feeder"
It also works with base modifiers and base nouns (intransitive verbs):
pan tiku - "killer" (thing that causes others to die)
pan pani - "thing that makes others liquid" eg. a blender