anpa, insa, monsi and sewi

nouns
Although you might be tempted to use these words as prepositions, but they are not.

ona li lon sewi mi.		He is above me.
pipi li lon anpa mi.		The bug is underneath me.
moku li lon insa mi.		Food is in my stomach.
len li lon poka mi.		The clothes are at my side.

So you see, these words as used here are nouns, and mi is a possessive pronoun meaning "my". And since these words are merely nouns, you must still have a verb; in the above examples, lon is acting as the verb. Don't forget to include a verb!

Since these words aren't prepositions, they are free for other uses, just like any other noun/adjective/verb:

monsi as a body part

monsi

back, butt

anpa as a verb

mi anpa e jan utala.

I defeated the warrior.