La tendeno estas apud la muskolo.

A word-by-word breakdown is:

• la = the
• tendeno = tendon
• estas = is / are / am
• apud = next to / beside
• la = the
• muskolo = muscle

So the structure is very direct: The tendon is beside the muscle.

In Esperanto, nouns normally end in -o.

So:

• tendeno = a noun, tendon
• muskolo = a noun, muscle

This is one of the most regular parts of Esperanto grammar. If you see a word ending in -o, it is usually a noun.

Related patterns:

• -a for adjectives
• -e for adverbs
• -i for infinitive verbs

La is the definite article, meaning the.

It is used before both nouns because both are being spoken of as specific things:

• la tendeno = the tendon
• la muskolo = the muscle

Unlike English, Esperanto has only one article of this kind:

• la = the

There is no separate word for a or an. So if you remove la, the noun often becomes more general or indefinite depending on context:

• tendeno = a tendon or just tendon
• muskolo = a muscle or just muscle

Estas is the present-tense form of esti, which means to be.

So:

• esti = to be
• estas = is / are / am

Esperanto uses the same present-tense form for all persons:

• mi estas = I am
• vi estas = you are
• li estas = he is
• ŝi estas = she is
• ĝi estas = it is
• ili estas = they are

In this sentence, estas links the subject la tendeno with its location apud la muskolo.

Apud is a preposition meaning beside, next to, or nearby at the side of.

So apud la muskolo means beside the muscle or next to the muscle.

It suggests physical closeness. In anatomy, that makes good sense.

A learner may compare it with other prepositions:

• apud = beside, next to
• sur = on
• sub = under
• en = in
• ĉe = at, by
• proksime de = near

Apud is often more specifically at the side of than ĉe, which can be more general.

Because apud is a preposition, and here la muskolo is simply the object of that preposition.

So:

• apud la muskolo = beside the muscle

There is no direct object here, so no accusative -n is needed.

The -n ending is most commonly used for:

• direct objects
• sometimes direction with certain prepositions

But in this sentence, la muskolo is just part of a prepositional phrase, so plain muskolo is correct.

Yes, grammatically you could, but the meaning changes.

• apud la muskolo = beside the muscle
• apud muskolo = beside a muscle or beside muscle in a more indefinite sense

In many real contexts, especially anatomical ones, using la sounds more natural if a particular muscle is meant.

So the original sentence sounds like it refers to a specific tendon and a specific muscle.

Yes, Esperanto word order is fairly flexible, though some orders are more neutral than others.

The most neutral order here is:

• La tendeno estas apud la muskolo.

You could also say:

• Apud la muskolo estas la tendeno.

That puts more emphasis on the location first, something like Beside the muscle is the tendon.

Because there is no accusative marker here, word order changes can affect emphasis more than grammar. The original sentence is the clearest and most ordinary version.

A simple English-friendly guide is:

• La ≈ lah
• tendeno ≈ ten-DEH-no
• estas ≈ ES-tahs
• apud ≈ ah-POOD
• la ≈ lah
• muskolo ≈ moos-KOH-lo

The full sentence is pronounced roughly:

lah ten-DEH-no ES-tahs ah-POOD lah moos-KOH-lo

A key Esperanto pronunciation rule: the stress normally falls on the second-to-last syllable.

So:

• ten-DE-no
• ES-tas
• a-PUD
• mus-KO-lo

Yes, both nouns are singular:

• tendeno = tendon
• muskolo = muscle

To make them plural in Esperanto, add -j:

• tendenoj = tendons
• muskoloj = muscles

So a plural version could be:

• La tendenoj estas apud la muskoloj. = The tendons are beside the muscles.

Notice that estas stays the same. The verb does not change for singular or plural.

It is a normal Esperanto word. Like many Esperanto words, it is built from internationally familiar roots, so it may look recognizable to speakers of English and other European languages.

That is common in Esperanto vocabulary:

• muskolo resembles muscle / muscul-
• tendeno resembles tendon / tendin-

Even when words feel familiar, Esperanto still applies its own regular spelling and endings, such as the noun ending -o.