Apposition: la urbon Parizon

Apposition is two nouns side by side for one thing, with no word between them: la urbo Parizo, mia amiko Petro. Both nouns fill the same slot in the sentence, so both take the same ending. When that slot is the object, the -n lands twice.

Where English says the city of Paris or the month of May, Esperanto needs no linking word: la urbo Parizo, la monato majo. (For affixes used as words, ilo, aro, eta, see affixes that are also words.)

The case echoes

The two nouns do not describe each other: they are each other. La urbo and Parizo name one place, so they do one job and wear one ending.

With a language name you will also meet the bare form, la lingvon Esperanto, the name treated as a label; the echoed form is the regular one.

The plural echoes too, and a comma changes nothing:

• Mi salutas miajn amikojn, la esperantistojn. - I greet my friends, the Esperantists.

English speakers often drop this -n, because English has no ending to drop: I saw the city of Paris sounds finished after city. Hear the two nouns as one phrase with one job.

When it does not echo

The second noun copies the first. Where the first has no -n, neither does the second.

After a preposition. A preposition is followed by the plain form, so there is nothing to copy:

The last line is the direction -n: en with motion puts -n on the first noun, so the second copies it.

A name kept in its own spelling. Parizo, Londono and Petro have Esperanto endings and take -n. A name left as it is spelled at home has nowhere to put one, so the title takes the -n and the name stays:

A book title or a quoted word is being named, not used, so it keeps the shape it came with.

ni ĉiuj, vi ambaŭ, li mem

Ĉiuj after a pronoun names the same people, so it copies the pronoun's ending:

Tri stays tri because numbers take no endings. Two more words never change, however the pronoun before them does:

• Li vidis nin ambaŭ. - He saw us both.
• Mi vidis lin mem. - I saw him himself.