The word elements O, A, E, I, AS, IS, OS, US and U are word class endings. They are very important for word building. There are also the endings J and N. They are not important in word building.

Particles are already words by themselves:por, mi, jam, eĉ, tiam, anstataŭ, je, jes and others.

Most word elements are roots. Each roots in itself has a meaning, but a root can't appear by itself as a word. It needs a word class ending.

• Some roots show people, persons ie.: AMIK, TAJLOR, INFAN, PATR, SINJOR, VIR...
• Other roots indicate animals,ie.: AMIK, TAJLOR, INFAN, PATR, SINJOR, VIR...
• Others are plants,ie.:ARB, FLOR, ROZ, HERB, ABI, TRITIK...
• Some roots are tools,ie.: KRAJON, BROS, FORK, MAŜIN, PINGL, TELEFON...
• Many roots are names of actions, ie.:DIR, FAR, LABOR, MOV, VEN, FRAP, LUD...
• Other roots are names of characteristics or qualities ie.:BEL, BON, GRAV, RUĜ, VARM, ĜUST, PRET...

There are many different groups and categories, not just the ones just mentioned. Some roots are difficult to classify, some have several meanings, others has a very special meaning, but all have some kind of meaning.

To use the root correctly with various endings, it's important to understand the root's meaning. The importance of the root's meaning is shown effectively with the classic example of the roots KOMB (comb) and BROS (brush).

The two verbs kombi (to comb) and brosi (to brush) have very similar meanings. They both show an action, and the two actions are very similar. But if you turn them into nouns, they are suddenly completely different.

The explanation for this drastic change is the fact that the roots already have meanings. KOMB (comb) is the name of a certain action, while BROS (brush) is the name of a certain implement. Therefore, with O-endings, they represent the names of an action and an implement, respectively — very different things. But with a verb ending, they both have the meaning of an action. In this case, KOMB hardly changes, because it is already an action, by nature. BROS, though, changes, and shows the action that one normally does with a brush.

If a noun is desired for the action that one does with a brush, a compound word must be used: bros-ad-o. Similarly, if you need a word for the tool used for combing, a compound form must also be used: komb-il-o.

There are many of these root pairs where the meaning of the verb form is similar while the O-form is different. The explanation in every case is that the meaning of the roots is different. Here are some examples: bati — marteli, haki — pioĉi, servi — sklavi, kudri — tajlori, regi — reĝi, kaperi — pirati, viziti — gasti. Similarly one can find pairs where the A-form is similar while the O-form is different, e.g.: eleganta — danda, nobla — nobela, lerta — majstra, kuraĝa — heroa, proksima — najbara, dolĉa — miela. Check out the meaning of the corresponding O-form in a dictionary.

One can say that there are various basic words which are a departure point for word building. With BROS/ we start with the basic word broso which is the name of the tool from which we can form the verb brosi (by changing the O to I). However with KOMB/ the basic word is kombi(which of course names an action.) From kombi we can create a noun denoting an action kombo (by replacing the I with O), and the word for the appropriate tool, kombilo (by adding the suffix IL and an O-ending.)

Action roots are often called verbal roots or roots with verbal characteristics, because we easily see the verb as the underlying form. Therefore action roots normally appear in dictionaries in verbal form.

Roots of quality are often called adjectival or having adjective characteristics because we see the A-ending as its basic form. Therefore roots of quality are normally shown as adjectives in dictionaries. Also roots which most often appear with the E-ending are traditionally called adjectival.

Roots neither of quality nor of action are often called substantives or nounlike. They are normally shown as nouns in dictionaries.

O-ending

The ending O does not add anything to the meaning of the root. A noun is simply the name of a particular thing.

A-ending

The ending A shows that the word is used to describe something. A = "related to the thing in question, like the thing, etc.:

When the root of an adjective has the meaning of a quality, the adjective normally shows a quality. Those adjectives don't vary much according to context:

When the root of an adjective doesn't have the meaning of a quality, the adjective can be used to show different kinds of descriptions. Generally, the meaning of adjectives of that sort varies greatly with context:

When the root of an adjective has the meaning of an action, the adjective can have a wide range of meanings. It can mean "related to the action in question", and so forth. Adjectives of that type can also be similar to -ANT- participles or -INT- participles with an A-ending:

Some of those adjectives, however, have a very specific meaning to describe quality.

Some of these types of ajdectives are similar to the passive participle: komplika ≈ komplikita. In the simple adjectival form the action of the root is either of no interest, or it didn't occur; only the quality is important. Sometimes the quality exists entirely by itself. The corresponding participle forms always show that this action did occur or is occurring.

Many think that some of these adjectives, especially korekta should be avoided when used to to describe a characteristic. Some even think that this usage is downright wrong. According to them komplika should only mean “being complicated” or “relating to complexity”, and korekta, according to them, should only mean “in the act of correcting” or “realted to correction”. But some of these adjective are never critized, althoug they are quite similar. However this type of word building has been familiar to Esperanto since the beginning, and abundant examples exist from many authors from Zamenhof to the present. In some cases the ambiguity of these type of adjectives could cause misunderstanding, and at that time one should reword the sentence, but this is also the case for any word with several meanings. The roots of these adjectives are action roots, but because the meaning is one of quality one might think that the roots are qualitative. In that case there is the risk of erroneously adding and IG-suffix to the simple verb forms using kaŝigi instead of kaŝi, komplikigi instead of kompliki, korektigi instead of korekti, etc. These IG-forms do however have another very specific meaning: kaŝigi = “to make someone hide something”, vekigi = get someone to wake somebody”, komplikigi = “to cause somebody to complicate something” etc. One should also not think that the simple verb forms have the meaning of “being so”. Korekti does not mean “to be error free”, but “to make error free”. Kompliki doesn not mean “to be unnecesarily complicated”, but “to make unnecessarily complicated”.

E-ending

Word creation by using the E-ending is very similar to the use of the A-ending. E = "relating to the matter, in that way" etc.:

Verb endings

I = "to perform a certain action (or be in a certain state) which closely relates to the meaning of the root". (The ending I here represents all verbal endings: I,AS,IS,OS,US and U.)

An action root with a verb ending always has its own particular meaning:

Verbs made from a non-action root shows an action which somehow is close to the meaning of the root. Sometimes it is quite obvious what this action is, but sometimes one might hesitate. With many non-action roots tradition has already determined the meaning resulting from the addition of the verbal ending, but some roots are not being used in a verbal form and it has not been decided what meaning they would have as a verb.

If a root in itself shows quality or state, the resulting verb normally means "to be like that" or "to act with that quality":

Normally that type of verb does not mean "become such" or "cause such". With qualitative or stative roots one uses the suffixes IĜ and IG to come up with that meaning.

If the root shows a tool, or appliance or something similar, the verb normally means "to use that tool in its customary purpose":

If the root shows a substance, the verb normally means "to provide that substance":

With these types of words the suffix UM is sometimes used unnecessarily.

If the root shows a person, a human being, the root normally means "to act like that person", "to play the part of that person":

Roots designating animals and various phenomena related roots in their verb form take on the meaning "to act like this animal or phenomenon":

Many roots of various types receive a verbal meaning, which can only be explained by the most general rule that their verbal meaning is somehow closely related to the meaning of the root.

Specifying preceding elements

One often combines roots (and particles) to create compound words. The most common type of compound word we call here a combination. Such a words consists of two parts: a main element which gives the general meaning of the word, and the specifying preceding element, which particularizes the general meaning.

Out of the main element ŜIP we can make, for example, the following combinations (always with a "neutral" O-ending):

The basic meaning of these combinations is always "ship". With various preceding elements we can distinguish different types of ships. The preceding elements are quite diverse. VAPOR shows the manner in which this type of ship is propelled, BALEN shows the end use of this type of ship, while AER shows location where it is used.

More often than not the preceding element distinguihes different species. Sometimes, however, it is not a question of species or type but of part of the main element,ie.: antaŭbrako (forearm)= "that part of the arm which is closest to the front of the body"; Orient-Eŭropo (Eastern Europe) = "the eastern part of Europe."

A combination behaves just like a single root. It can take any kind of ending: vaporŝipo, vaporŝipa, vaporŝipe, vaporŝipi; rondiro, rondira, rondire, rondiri; piediro, piedira, piedire, piediri; helruĝo, helruĝa, helruĝe, helruĝi.

New combinations can be made out of the combinations themselves:

Combinations of several roots can theoretically result in multiple meanings. There is no grammar rule which makes it clear that ŝarĝvaporŝipo is a ŝarĝ-vaporŝipo (a steamship for cargo) and not a ŝarĝvapor-ŝipo ("a ship which somehow relates to cargosteam, which is nonsense.) Through your own analysis you have to decide which of the theoretical possibilities is the correct one. Confusion on this point is rare in practice. In writing one can use a hyphen for clarity, as in ŝarĝ-vaporŝipo. Generally, combinations with more than three or four roots can be too difficult. Instead of vaporŝipasocimembrokunvenejo you might preferably say kunvenejo por membroj de vaporŝipasocio.

Interlinking endings

After a specifying preceding element you can put a linking O-ending to facilitate pronunciation or understanding of the combination:puŝoŝipo, aeroŝipo, sangoruĝo etc.

One does not use a linking element in those combinations where a preceding element most naturally becomes an adjective when separating the combination, ie. dikfingro (thumb) = "type of finger which usually is thicker dika than the other fingers." It is hardly possible to explain the meaning in a natural manner using the word diko. Therefore we don't say dikofingro, nor dikafingro, but when needed dika fingro. The same thing occurs with action words where the specifying preceding element shows a quality which results from the action: ruĝfarbi → farbi ruĝa, farbi tiel ke io fariĝas ruĝa; plenŝtopi → ŝtopi plena. In these combinations also one does not use a linking element. Also in combinations of action where the preceding element shows the manner of the action, one usually does not use the linking element, but instead separates the combination when necessary: laŭtlegi → legi laŭte.

Forms like nigra-blanka are not combinations, but two separate words written together to give a special nuance .

If the preceding element is a particle (a word which does not take an ending) one normally does not use a linking element. As required one may,however, use a linking E-ending: postsigno → postesigno(makes pronunciation easier), postulo → posteulo(makes comprehension easier). This however happens very rarely.

A preceding element consisting of a particle can have endings other than E, but only when that adds necessary meaning: unuaeco [uniqueness] = "the quality is unique" (unueco [unity] = "the quality is like one"), antaŭeniri = "to go forward" (antaŭiri = "to go before something"). The link EN (E+N) is used sometimes also used with preceding elements from roots: supreniro, ĉieleniro (or ĉieliro), hejmenvojaĝo (or hejmvojaĝo).

E as a linking ending occurs sometimes when the preceding element is the root MULT:multe-nombro.

In combinations made up of an action root plus POV,VOL, or DEV, one normally uses "I" as a linking ending:pagipova, vivivola, pagideva. It is better to explains these forms as phrase words. One can also use O in those words: pagopova, vivovola, pagodeva. Then they are combinations, but O en these types of words is not as customary. In principle one could also use them without any linking element at all: pagpova, vivvola, pagdeva, but those forms are hardly used in practice.

If the main element is a suffix, or if the preceding element is a prefix, then one does not use the linking ending .

In another type of compound, the phraseword, one uses a linking element (interfix) according to other rules.

Particles in combinations

Some particles are often used with endings. These combinations can also take a specifying preceding element.

Explanatory combinations

Often the meaning of a combination can be explained by a preposition:

But not all combinations can be explained like that. Some need a more complicated explanation:

Many unexpressed ideas can be hidden in a compound word. The compound consists of a combination of a main element, which gives the basic meaning, and a preceding element which shows some type of characterization, but the combination is not the full definition of the meaning. In effect, the meaning of a combination depends not only on the meaning of its parts, but also on the tradition of the language.

One often hesitates, for example, between lada skatolo and ladskatolo, sovaĝa besto and sovaĝbesto, dikfingro and dika fingro. Often it is possible to use either form regardless, but there is nevertheless an essential difference between a combination and the two word expression with adjective and noun. When using a combination you are creating a word for a special idea, for a certain type of thing. You are showing some idea which for some reason is regarded as different and in need of a separate word. On the other hand, when a noun is used with an epithet we are showing only an occasional or fortuitous characteristic.

So a specifying preceding element shows the characteristics of the species or type, not of the individual. An epithet usually describes the individual but may also describe the species depending on context. Therefore one can also use epithets to name species. One can say dika fingro instead of dikfingro. One can say vapora ŝipo instead of vaporŝipo. It is possible to say sovaĝa besto instead of sovaĝbesto. But it doesn't work the other way around because not every dika fingro is a dikfingro, not every vapora ŝipo is a vaporŝipo, and not every sovaĝa besto is a sovaĝbesto.

There is often the misunderstanding that one cannot make a compound in which the preceding element is a root of characteristic. In fact, such words are constantly being formed, for example:altlernejo, altforno, dikfingro, sekvinberoj, solinfano, sovaĝbesto, sanktoleo, and many others. They are all correct. But one cannot simply shove together a noun with an adjectival epithet if one does not intend to create a more specialized meaning. Don't say belfloro if you simply mean bela floro.

Many think that one cannot create combinations whose main element shows action while the preceding element shows an object of that action, for example:leterskribi, voĉdoni, domkonstrui. This however is not correct. In these combinations the preceding element is not an ordinary object, but shows a characteristic of a type of action. These types of combinations differ significantly from the two word combinations skribi letero(j)n, doni voĉo(j)n etc. In skribi leteron the grammatical object shows a concrete object which results from writing, while in leterskribi LETER only characterizes the type of writing. The meaning of some similar verbs have a nuance of attempt: fiŝkapti = "to try and catch fish". Those type of verbs can be explained as frazetvortojn. (short phrases condensed into a word)

Making a short phrase into a word

A phrase (any group of words belonging together)can be shoved together into a compound by addition of some following element. The result is a frazetvorto (phrase-word). From the original phrase only the most important words are retained. Endings and other less important elements are usually dropped off. For ease of pronunciation or comprehension one may however preserve the word class ending of the original phrase, but J-endings and N-endings are not kept.

When a short phrase is expressed using a verb ending or an O-ending, the ending represents a sort of hidden idea. The meaning of the ending must be learned separately for every word of that type:

The phrases put into a word are also used as prefix elements of combinations. The main element is usually a suffix:

A more extreme and rarer form of compounding is making a word from a quote. In this type of word building which is similar to making a word from a phrase, a word is made from an entire statement (real or imagined). In those cases the whole words of the citation are retained, inclusive of their endings: "Vivu!" → [vivu]-(krii)-I → vivui= to shout "vivu!", to greet someone with the cry "vivu!". Note that the U-ending stays. Ordinary words can't have two word class endings one after the other. But vivui is not an ordinary word. It is a quotation made into a word and the U-ending is absolutely necessary to the meaning. "Ne forgesu min!" → [ne forgesu min]-(floro)-O → neforgesumino= Forget-me-not, a flower of the genus Myosotis (la name comes from the blue color of the flour which is a symbol of fidelity in love)

Affixes

A small group of roots (around 40) are called affixes. They are roots that are used mainly in compound or constructed words. Some of them are suffixes – affixes used at the end of a word, appearing after other roots. Others are prefixes – affixes coming at the beginning of a word, before other roots.

Mainly, tradition has decided which roots are considered affixes. However, one could say that an affix is a root for which special word building rules are valid. Some of the traditional affixes, by this definition, are ordinary roots. In the preceding explanations of ordinary word building there were some examples with roots which are traditionally called affixes.

The majority of suffixes function as the main element of a combination. What stands before the suffix is a specifying prefix. But for the majority of suffixes there is a special rule which limits the possible relationship between the main element and the prefix. For ordinary roots there are no such limits.

The suffixes AĈ, ĈJ, EG, ET, IN, NJ and UM do not at all behave that way. Word created with this suffixes are neither combinations nor phrasewords. These suffixes therefore are true affixes.

The majority of prefixes function as a specifying preceding element of a combination. That which stands after the prefix is the main element, whose meaning becomes more specific through the prefix. But usually there is a special rule which limits the possible relationships between the prefix and the main element.

However the prefixes GE and MAL do not behave in that way. GE and MAL change the meaning of the following element so radically that it can not be explained as an ordinary combination (nor as a word phrase). Therefore GE and MAL are true affixes.

In principle one can also use any affixial morpheme as an ordinary root. Some affixes are even quite commonly used that way. Others, ĈJ and NJ for example, are rarely used as ordinary roots. Some examples of that usage appears in the following explanations about various affixes.

With affixes one normally does not use a linking ending such as in dormoĉambro. For example, we do not say ekokuri, eksosekretario, ŝipoestro. A linking element is used with affixes only when it is more or less necessary to the meaning or for comprehension, as in unuaeco, antaŭenigi, posteulo.

The participial suffixesANT, INT, ONT, AT, IT kaj OT behave in a particular way.

Some roots, which are ordinarily not classified as affixes, behave nonetheless in a matter similar to prefixes or suffixes. These may be referred to as affix-type elements.