When we wish to express "motion towards" something, and the preposition
does not of itself express it, "n" is added to the noun or pronoun, as
in the case of adverbs (see Lesson 12), "Li estas en la domo", He is in
the house; but, "Li iras en la domon", He is going into the house.

NOTE.--There are three cases in which the noun or pronoun takes "n".
(i.). When it is the "direct object" of the verb, as "Mi vidis lin",
I saw him. (ii.). To show "direction", as "Li iris en la gxardenon",
He went into the garden. (iii.). When the "preposition" is "left out".
This is usually done in the case of "dates" and expressions signifying
"duration" of time, as "Georgo Vasxington estis naskita la dudek-duan de
Februaro de la jaro mil sepcent tridek du", George Washington was born
the 22nd of February, 1732. "Vi restos tie cxi la tutan vivon (dum la
tuta vivo)", You will remain here your (the) whole life.

All the prepositions whose meaning allows of it can be used as
adjectives, adverbs, etc., by adding the proper endings, as from
"antaux", before, we get "antauxa", former, "antauxe", formerly or
previously, "antauxen", forward.

Prepositions are also joined to other words, and to prefixes or
suffixes, as "antauxdiri", to foretell; "apudmara urbo", a seaside town;
"senigi", to deprive of.

Sometimes the preposition is both prefixed to the verb and used after it
before the noun, as "Li eliris el la domo, kaj eniris en la gxardenon",
He went out of the house, and entered into the garden.