Some elements of the language that aren't ordinarily called affixes are nevertheless used in word building in a particular manner, according to specific rules. The word building is almost always done according to the ordinary rules of compound words and phrases as words, but with some special detail. These elements may be referred to as affixes, or affix-like elements. Other elements can also be used in compound words, used like affixes, although they follow the full set of rules normally used for word building. These elements can also be referred to as affixes, or affix-like elements.

Affix-like roots and compounds

Here are several examples of ordinary roots that are often used like affixes.

FIN

FIN is often used as a prefix, instead of prefix-like use of el to show the completion of an action: finkanti, finfari, finmanĝi.

HAV, PLEN, RIĈ

The roots HAV (have), PLEN (full), and RIĈ (rich) can be used as suffixes to add precision to the meaning of an adjective: barba → barbhava, trua → truhava, manka → mankohava, ama → amoplena, brua → bruoplena, flora → florplena, fuma → fumoplena, ora → ororiĉa, herba → herbriĉa, senta → sentriĉa.

KELK

KELK as a prefix shows multiplication by an undefined but small number (greater than one): kelkdek = "some tens", kelkcent = "some hundreds", kelkmil = "some thousands". Pay attention to the accent: kElkcent, kElkmil. KELK is not a particle, but a root. Therefore these words cannot be written separately. Do not write kelk dek, kelk mil, but kelkdek, kelkmil. It is always possible to instead say and write: kelkaj dekoj, kelkaj miloj etc.

KELK, when used as a suffix, shows the addition of an undefined number (more than one): dekkelke = "ten and some", tridekkelk-jara = "having thirty and a few years", "thirty-something".

Sometime a prefix usage of KELK is used with the meaning of "about": kelkmil = "around a thousand". This collides with the previously shown usage by Zamenhof, and this usage is not recommended.

KELK is used as a prefix also among table words ending in I to emphasize the indefinitness: kelkiuj = "some, some ones", kelkiom = "a few, some". The occasionally used form kelkiu (without J) is self-contradictory. Iu shows precisely one individual, while KELK shows more than one.

ON- words

Compound words with the suffix ON are often used as prefixes: duonhoro = "half an hour", kvaronlitro = "a quarter of a litre", milonmilimetro = "a thousanth of a millimetre", trionparto = "a third of a part". It is possible to create ordinary combinations instead, for example: horkvarono (= "a quarter hour"): Pasis certe horkvarono, antaŭ ol la floreto povis denove rekonsciiĝi. Forms like horkvarono are, however, extremely uncommon.

DUON sometimes has a special meaning when used as a prefix: "about halfway, incomplete, almost": duonnuda = "almost nude", duonkuirita = "not completely cooked".

With words for relatives, DUON has two special meanings. There, it shows a familial relationship between only one of the parents, and also a relationship created by remarriage: duonfrato (half brother) = 1. a brother with whom one has only one common parent, 2. the son of a half mother or father; duonfilo (stepson) = a son of one's husband or wife; duonpatro (stepfather) = the new husband of a mother; duonpatrino (stepmother) = the new wife of a father.

VIC

VIC is used as a prefix to show a thing or a person that replaces or can replace something or someone: vicprezidanto = "substitute president", vice president; vicdirektoro = "substitute director", vice director; vicrado = "spare tire".

The root VIC can also be used as a prefix to show a family relationship caused by remarriage, akin to the English use of "step": vicpatro, vicfilo, vicfrato. In these DUON-words, which can have both meanings of a familial DUON (half), VIC should preferably be used for a relationship resulting from a remarriage, and DUON only for a true half relationship.

VIR

VIR is used as a prefix to show male sex. It can be compared with the suffix IN. VIR can therefore only be used with a root that can have a gender, and only with words that are not inherently male.

VIR is used as a prefix mainly for animal words: virĉevalo, virkato, virbovo, virhundido, virbesto.

VIR can also be used like a prefix on words for people: virhomo, virprezidanto, virsekretario. But VIR is normally used as an adjective for indicating people: vira homo, vira prezidanto, vira sekretario.

The root VIR, however, is sometimes left out even when a male animal or human is being referred to.

Note that the word viro (man), used independently, always means "adult male person", while VIR used as a prefix only shows the male sex (not a person being human, nor adult). The word vira (manly, related to men) sometimes only shows male sex and sometimes indicates that something is human or adult, depending on context.

Use of prepositions as affixes

Words using a preposition as a prefix are most often words based on phrases. The preposition is used as a prefix on the word that it would relate to in a phrase:

A preposition used as a prefix can also be a clarifying element to begin a combination. In these words, the preposition is not a role marker for the following element; instead, it relates to something else:

When this sort of word is used in a sentence, the preposition used as a prefix is often repeated before the expression to which it actually relates to: Li eliris el la dormoĉambro kaj eniris en la manĝoĉambron. But often, we do not repeat the preposition before the word it relates to; instead, we use another preposition: Ĝi parolas nur pri tiaj instruoj, kiuj ne kontraŭparolas al la scienco. Al instead of a repetition of kontraŭ. What the prefix preposition actually relates to can often appear as an object of this kind of verb: La belan Saran li jam kelkfoje ĉirkaŭiris. = Ĉirkaŭ la bela Sara li jam kelkfoje (ĉirkaŭ)iris. But very frequently, the object of this verb is something else entirely, without a direct relationship to the preposition used as a prefix: Alportu al mi metron da nigra drapo.

El

El can be a completely normal preposition used as a prefix, in combinations and phrase words, for example: eliri (combination) = "to go out of something", elbati (combinaton) = "to hit something out of something", el (la) lito → ellitiĝi (phrase word) = "to get up out of bed".

But el used as a prefix in combinations is also used with the special meaning of "completely, totally, until ready, until a result, until breakage, until disappearing":

Some of these el words receive a special (figurative) meaning:

If there is a risk of confusion between the usual meaning of el and its special meaning of ending or completion, some other prefix should be used for the meaning of "to the end". In that case, roots such as, for example, tra, for, SAT, and FIN may be used. The root or particle being used should always be used in a context that makes sense; for example: trabori, trakuri, forkaŝi, satmanĝi, finkanti, finfari, finmanĝi etc. An expression with several words can also be used to convey the correct meaning; this is often the best solution: legi ĝisfine, kuri tra la tuta urbo, manĝi ĝis sateco, kanti ĝis la fino, kanti la tutan kanton etc.

Pri

In phrase words (with an A-ending or E-ending), pri is used as a prefix in an ordinary way, for example: pri amo → priama = "having to do with love", pri nutro → prinutra = "relating to nutrition".

In combinations, a prefix-like use of pri makes transitive verbs. It is used to make an intransitive verb transitive, or to make a new transitive verb out of a verb that is already transitive. Normally, this sort of pri verb has an original pri adject as an object:

In some situations, this kind of pri verb has an object, which is originally a de adject or an al adject, rather than a pri adject. In these verbs, pri loses its own meaning, and is used only to change the role of the word in the sentence. Pri is used in this manner mainly in a few traditional verbs:

Use of pri as a prefix can be used in some situations to give the verb a new meaning that relates somehow to the original meaning:

In this usage, pri (about) is similar to the suffix UM.

Other affix-like particles

Aside from prepositions, many other particles are used like prefixes in various ways. Some of the most important examples of this usage are discussed below.

Ĉi

The word ĉi, showing location or proximity, is frequently used as a prefix in phrase words with an A-ending or an E-ending. Normally, a hyphen is used after ĉi for clarity:

Note that ĉi is an independent word in tiu ĉi, ĉi tiu, tie ĉi, ĉi tie etc. Don't use a hyphen in those cases.

Fi

The interjection fi is often used as a prefix with the meaning "unlikable, abominable". The prefix usage of fi shows subjective indignation or moral condemnation of the word to which fi is attached:

The prefix fi and the suffix AĈ are similar. Fi is more subjective. It shows indignation or dislike. AĈ is more objective. It shows unsuitability and poor quality.

For

The particle for, used to show location and movement, is often used as a prefix with action words: foriri, foriro, forkuri, forkurado, forfali, forĵeti, forŝiri, forpermesi, fortimigi, forargumenti, forbuĉi, fordormi, foresti, foresto. These combinations are frequently used in normal speech. De is also often used in these words: forŝiri ≈ deŝiri, forpreni ≈ depreni, fortranĉi ≈ detranĉi. But for gives a stronger meaning.

Mem

Mem used as a prefix has two different meanings: 1. "without the help of another": memvole, memlerninto, memdisciplino, memstara, memkompreneble. 2. "to oneself, about oneself, oneself": memestimo, memamo, memdefendo, memmortigo, memportreto, memofero. If the meaning is "oneself", sin can also be used as a prefix.

Ne

The use of ne as a prefix shows absence, lack of something (for example, of a quality): neĝentila (impolite), nelonge (not long), nefermita (not closed), nematura (immature), nelerta (unskilled), nekomprenebla (incomprehensible), nelegeble (illegible), nekredebla (unbelievable), nejudo (non-Jew) = "a person who isn't a Jew", ne-Kopenhagano = "a person who doesn't live in Copenhagen".

Sin

The pronoun si (oneself) with the N-ending is often used as a prefix instead of mem (self) for the meaning of "oneself": sinfido, sindefendo, singarda, sindona.

Sin as an independent word can only be used in the third person. But sin can be used as a prefix also for the first and second persons: Kontraŭ s-ro K. mi estos singarda. = Mi gardos min kontraŭ s-ro K.

Sin words are words that behave as short phrases, deriving from a short infinitive expression: sin defendi → [to defend oneself]-(action)-O → sindefendo (self defense) = "the action of defending oneself"

This sort of sin-word can take any kind of ending except a verb ending: sinfido, sinfida, sinfide. In order to use a verb ending, it's necessary to return to the original phrase, in which sin was a separate word. If sin doesn't refer to the third person, the words min (myself), nin (ourselves) or vin (yourself) are used instead, as appropriate.

In these words, the N-ending of sin is retained. Normally, however, the N-ending (like the J-endings) is omitted from the middle of compound words.