Esperanto has an extremely simple system of nouns, adjectives, and adverbs. There are no grammatical genders (non-living things are not arbitrarily determined to be a “he” or a “she”), and while there is something called the “accusative marker”, its use is really simple. The basic rule is:
Adjectives end in -a, e.g. amika, “friendly”.
Adverbs end in -e, e.g. amike, “in a friendly manner”.
Here are a few examples:
koro “heart” — kora “heartfelt, cordial” — kore “cordially”
loko “place” — loka “local” — loke “locally”
Sometimes a noun is derived from an adjective. Such nouns usually correspond to English -ness, -ity, or -ance/-ence, and the corresponding suffix in Esperanto is -eco:
fidela “faithful” — fideleco “faithfulness, fidelity”
aroganta “arrogant” — aroganteco “arrogance”
You may be asking yourself why we don’t simply change -a to -o in such cases. This would cause problems with adjectives that are already derived from a noun. The following examples should make the distinction clear:
viro “man” — vira “male, masculine” — vireco “masculinity, manliness”
For the sake of completeness, I should mention that there are two small classes of adverbs that do not have the suffix -e. There are a few common adverbs that consist of just one syllable, e.g. nur “only”, nun “now”, and a few that end with -aŭ, e.g. hodiaŭ “today”, preskaŭ “almost”. These are two rare examples of irregularities in the process of word formation in Esperanto (but there are still no grammatical irregularities).
The definite and indefinite article
La is the Esperanto equivalent of “the” in English, e.g. la mano “the hand”. There is no indefinite article in Esperanto (no “a”); “a hand” is translated simply as mano, without la.
It may seem strange at first to use a bare noun without any article preceding it, but the good thing is that you don’t have to care about the distinction between countable and uncountable (mass) nouns, which are a common source of errors in other languages. For example, English learners commonly say “an information” (as in “I found an interesting information”) because the word “information” is countable in most other languages.
In Esperanto, specified nouns are preceded by la, unspecified by nothing, no matter whether they are countable or not. If there are any adjectives, they go between the article (if there’s any) and the noun, just like in English. For example:
I write with the [my] right hand. Ĉi tio estas grava informo.
This is important information.
The plural -j
English plurals are not complicated, but they still exhibit a certain degree of irregularity. The plural of “goose” is “geese”, the plural of “man” is “men”, the plural of “ox” is “oxen”… In esperanto, the plural of every single noun is formed simply by adding the suffix -j to it. Since every noun ends in -o, every plural noun ends in -oj (pronounced “oy”, as in “boy”). A few examples:
loko “a place” — lokoj “places” — la lokoj “the places”
koro “a heart” — koroj “hearts — la koroj “the hearts”
Articles are used in the same way as for the singular, i.e. no article for unspecified nouns and la for specified nouns (i.e. in the same way as for English plural nouns).
What differs from English is that adjectives in Esperanto also have a plural form, formed by adding -j. If an adjective refers to several things or people, it has to end with -aj, not just -a. For example:
the interesting places Ili estas malgrandaj.
They are small.
This can be useful in a few cases where the English form is ambiguous, such as “rancid butter and milk”. Compare:
rancid butter and [non-rancid] milk rancaj butero kaj lakto
rancid butter and [rancid] milk
However, it is not necessary to be concerned with such details at the beginning. Even if you forget to use -j every now and then, you will be understood. Just try to remember that whenever an adjective refers to two or more things, it should always end with “aj”.
The accusative marker -n
Esperanto has the so-called accusative case, which marks the direct object of a verb. Don’t be afraid if it sounds scary—it’s nothing like the nightmarish Latin or Russian case system. Let’s take a look at the accusative in English:
I like her (not “I like she”)
he informs me (not “he informs I”)
she has them (not “she has they”)
“Him” is the accusative of “he”, “her” is the accusative of “she”, “me” is the accusative of “I”, and “them” is the accusative of “they”. Whenever an action is done directly to someone, the pronoun has to be in the accusative. It works in the same way for pronouns in Esperanto, but the accusative of every pronoun is formed by simply adding the suffix -n. The sentences above can be translated as:
mi ŝatas ŝin (not “mi ŝatas ŝi”)
li informas min (not “li informas mi”)
ŝi havas ilin (not “ŝi havas ili”)
The difference between English and Esperanto is that nouns in the accusative also have the suffix -n, for example:
I see the book. Mi ŝatas manĝaĵon.
I like food. Ŝi havas fraton.
She has a brother.
Adjectives that modify nouns that are in the accusative also take the suffix -n:
I see the large book. Mi ŝatas bonan manĝaĵon.
I like good food. Ŝi havas pli aĝan fraton.
She has an older brother. [literally "more old"]
Plural nouns and adjectives that are used as direct objects have two suffixes, -j and -n, and thus end with -ojn and -ajn, respectively:
I see the large books. Mi ŝatas bonajn manĝojn.
I like good meals. Ŝi havas pli aĝajn fratojn.
She has older brothers.
If a noun is connected to a verb via a preposition, there is no accusative marker (except for a special case we will discuss in a separate article), for example:
The book is on the table.
The accusative marker is used after a preposition if the preposition expresses a direction (e.g. la kato saltas sur la tablon, “the cat is jumping onto the table”). We will discuss this usage in more detail in another article.