Mono ne estas la sola rimedo.

Because mono here is being used as a general, mass-noun idea: money in general, not the money or one money.

Esperanto often leaves out the article when talking about something in a general sense:

• Mono estas grava. = Money is important.
• Akvo estas necesa. = Water is necessary.

So Mono ne estas la sola rimedo means money in general is not the only means.

In Esperanto, ne usually goes directly before the word or part of the sentence it negates. Here it negates the verb phrase:

• Mono ne estas... = Money is not...

That is the normal and expected placement.

Compare:

• Li ne venas. = He is not coming.
• Tio ne helpas. = That does not help.

Because sola means only or sole, and la sola rimedo means the only means.

In English, only means by itself would usually sound incomplete in this kind of sentence. You normally say the only means. Esperanto works the same way here:

• la sola vojo = the only way
• la sola respondo = the only answer
• la sola rimedo = the only means

So the article la is needed because we are talking about a unique thing: the one and only means.

Because sola is an adjective, and adjectives in Esperanto end in -a.

It modifies rimedo, so it has to be in adjective form:

• sola = only / sole
• rimedo = means, remedy, resource

Together:

• sola rimedo = only means

Because there is no accusative here.

After the verb esti (to be), the complement does not take -n. In this sentence:

• Mono = subject
• estas = verb
• la sola rimedo = predicate complement

So rimedo and sola stay in their basic forms:

• Mono estas rimedo.
• Mono estas grava rimedo.
• Mono ne estas la sola rimedo.

You do not use accusative after esti.

Rimedo is a noun meaning something like:

• means
• resource
• way of solving a problem
• sometimes remedy

The exact translation depends on context. It often refers to something used to achieve a goal or fix a situation.

For example:

• Tio estas bona rimedo kontraŭ streso. = That is a good remedy/way to deal with stress.
• Ni serĉas rimedon por solvi la problemon. = We are looking for a means/way to solve the problem.

So in this sentence, rimedo means a means or resource, not necessarily a medical remedy.

Because the sentence is talking about the only means, understood as a single supposed solution or resource.

• la sola rimedo = the only means
• la solaj rimedoj = the only means/resources

Esperanto uses singular and plural normally here. Even though English means looks plural, it can be singular or plural in English. Esperanto avoids that ambiguity:

• rimedo = one means
• rimedoj = several means

Yes, Esperanto word order is fairly flexible, because grammar is shown mainly by word endings rather than strict position.

These are possible:

• Mono ne estas la sola rimedo.
• La sola rimedo ne estas mono.

Both are grammatical, but they do not emphasize exactly the same thing.

• Mono ne estas la sola rimedo focuses first on money
• La sola rimedo ne estas mono focuses first on the only means

The original sentence is the most natural if you want to begin with money as the topic.

Not quite.

Mono ne estas la sola rimedo clearly means:

• money is not the only means

Without la, the phrase becomes less natural and the meaning changes or becomes unclear. Sola rimedo means an only/sole means, but in this sentence the intended idea is specifically the only means, so la is important.

So if your meaning is money is not the only means, you should use:

• Mono ne estas la sola rimedo.

Yes. Esperanto adjectives can come before or after the noun.

So you could say:

• la sola rimedo
• la rimedo sola

But the first one, la sola rimedo, is much more normal here.

Putting the adjective after the noun can sometimes feel more emphatic, poetic, or unusual depending on context. For everyday usage, learners should prefer la sola rimedo.

Usually it is treated like money in English: as a mass noun.

So you normally say:

• multe da mono = a lot of money
• iom da mono = some money

You do not usually use a plural monoj unless you mean different currencies, different sums in a special context, or you are speaking unusually.

In this sentence, mono is the normal form.

Because the sentence is making an identification or classification:

• money is not the only means

The verb esti (to be) is used when one thing is being described as another thing, or when you say what something is.

Structure:

• Mono = subject
• estas = is
• la sola rimedo = the only means

This is a very common Esperanto pattern, just like in English.

Yes — several very useful basics appear in just one short sentence:

• -o marks a noun: mono, rimedo
• -a marks an adjective: sola
• la is the definite article
• ne makes the sentence negative
• estas is the present tense of esti
• no -n is used after esti

So this sentence is a good example of a simple Esperanto statement with a subject, negation, a verb, and a predicate noun phrase.