The Fundamento defines ci and cia as follows:

ci tu, toi, | thou | du | ты | ty.

ci'a ton, ta | thy, thine | dein | твой | twój.

Unfortunately, I've never actually seen ci used anywhere. I've seen it described as impolite, but most of the explanations as to why it's impolite tend to hinge on English "thy" and Russian "ты" being considered sarcastic or overly personal in most contexts.

However, I think these explanations might be oversimplifying the issue; this is Esperanto, and the connotations in other languages wouldn't necessarily carry over. Exercise 16 in the Fundamento contains the following line, suggesting not to use ci, but without any explanation as to why:

Ci skribas (anstataŭ „ci” oni uzas ordinare „vi”).

This does however suggest that ci didn't fall out of favor, and was never a common usage. Is there ever a good reason to use ci? If so, in what context, and if not, why?

up vote 14 down vote accepted

You should use ci about as often as you would use thou in English. Or less.

The purpose of ci was to provide an alternative, singular form of vi for use in translations (or pseudo-translations), when a sudden change in the choice of pronoun has to be rendered.

For example, in Kastelo de Prelongo, the language spoken by the characters is French, which contains the pair vous (polite) — tu (informal or rude). So we read:

Baraktante, ŝi ekkriis: "Viktoro Linŝardo!"

"Jes, belulino mia, Viktoro Linŝardo kiu cin amas, kaj kiu tion ekpruvos al ci. Ĉar mi ne povas esti cia edzo, mi fariĝos cia amanto: la afero estos sama."

Tiu malĝentilega cidiro impresis Matildon eble pli dolore ol la restaĵo.


Struggling, she cried out: "Victor Linchard!"

"Yes, my beautiful girl. Victor Linchard who loves thee, and who will prove it to thee. As I cannot be thy husband, I shall become thy lover: it will amount to the same."

That monstrous thouing made a more painful impression on Matilda than all else.

The use of ci is very brief; thereafter, the author renders tu as vi on the understanding that you now know how things stand between them.

However, a switch to thou in English now signifies an exaggerated increase in formality, whereas in the past it represented a decrease in formality: and that could be either a good thing or a bad thing. Other languages have different habits. In other words, the precise significance of ci depends on minutiae of the situation and the culture. This makes it a bad fit for general use in Esperanto.

In the Unua Libro (the first book about Esperanto from 1887), ci doesn't appear at all. Later Zamenhof introduced it in order to be able to render in translated works the distinction that most European languages make between a polite and a familiar second-person pronoun (tu-vous in French, Du-Sie in German, ты-вы in Russian, tú-usted in Spanish). However he made it very clear from the outset that it should only be used in translation and is not intended for actual usage in Esperanto. This is why he wrote "anstataŭ „ci” oni uzas ordinare „vi”" in the Fundamento.

Despite Zamenhof's recommendation, some people started to use ci as a second-person pronoun to be used with close friends, comrades, family members etc. But this usage never really took on, and is only practiced in some very small groups, especially among some people in SAT-Amikaro, the French section of the left-winged Esperanto labour organization SAT.

If you use ci, you risk either not being understood, or being looked at as a weirdo.

So basically you should never use ci, unless you are translating from a language which distinguishes between a polite and a familiar second-person pronoun (and even then, you might want to prefer other ways of rendering the distinction in Esperanto, for example by the use of the given name vs. the surname).

I use Esperanto almost every day. I never use "ci", though I have heard it used many years ago in left wing (SAT) circles in Bordeaux. To show friendliness, I usually add a word, such as "Kiel vi, amiko?"

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