La sola folio velkas.

La is the definite article in Esperanto, equivalent to the in English.

So la sola folio means the only leaf or the lone leaf, not just a leaf.

A few useful points:

• Esperanto has only one definite article: la
• It does not change for gender, number, or case
• Esperanto normally has no indefinite article, so folio can mean a leaf or just leaf, depending on context

Examples:

• folio = a leaf / leaf
• la folio = the leaf
• la folioj = the leaves

In Esperanto, nouns normally end in -o.

So:

• foli- = the root
• folio = leaf

This is one of the most basic patterns in Esperanto:

• -o = noun
• -a = adjective
• -e = adverb
• -i = infinitive verb

Related examples:

• floro = flower
• granda = big
• bele = beautifully
• kreski = to grow

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

Here sola describes folio, so it must be in adjective form:

• sola = sole, only, single, lone

Compare:

• sola folio = a lone / only leaf
• sole = only, solely, alone in an adverbial sense

So in this sentence, sola is correct because it modifies the noun folio.

In Esperanto, adjectives agree with the nouns they describe.

That means they match in:

• number: singular or plural
• case: especially whether they take -n

Here both are singular and neither is accusative, so we get:

• la sola folio

If it were plural:

• la solaj folioj = the only leaves

If it were accusative:

• Mi vidas la solan folion. = I see the only leaf.

This agreement is very regular and helps make sentence structure clear.

It can suggest any of those, depending on context.

In la sola folio, sola often means:

• only = there is just one
• single = one in number
• sometimes lone = standing by itself

Because you said the meaning is already shown to the learner, the main grammar point is that sola is an adjective. The exact English translation may vary a little depending on context, but the Esperanto structure stays the same.

-As is the present-tense verb ending in Esperanto.

So:

• velk- = the verb root
• velkas = is wilting / wilts

Esperanto verbs do not change according to person or number. That means:

• mi velkas = I am wilting
• vi velkas = you are wilting
• la folio velkas = the leaf is wilting
• ili velkas = they are wilting

The tense ending stays the same.

Useful tense endings:

• -as = present
• -is = past
• -os = future
• -us = conditional
• -u = command / volitive
• -i = infinitive

Both can be correct, depending on context.

Esperanto -as marks the present tense, but it does not force the same distinction English makes between:

• wilts
• is wilting

So velkas can correspond to either simple present or present progressive in English.

In many contexts, is wilting sounds more natural in English for a process happening right now, which is why that translation is often chosen.

No, velki / velkas is normally intransitive here.

That means the subject itself undergoes the action or change:

• La folio velkas. = The leaf is wilting.

There is no direct object because the leaf is not wilting something else.

If you wanted a causative idea, Esperanto can build that very neatly:

• velki = to wilt
• velkigi = to cause to wilt, to make something wilt

So:

• La folio velkas. = The leaf is wilting.
• La suno velkigas la florojn. = The sun is making the flowers wilt.

Because there is no direct object, and there is no motion-toward expression here.

The -n ending in Esperanto is mainly used for:

1. the direct object
2. sometimes direction toward a place

In La sola folio velkas, la sola folio is the subject, not the object, so no -n is needed.

Compare:

• La sola folio velkas. = The only leaf is wilting.
• Mi vidas la solan folion. = I see the only leaf.

In the second sentence, folion gets -n because it is the direct object of vidas.

Because that is the most common and neutral position in Esperanto:

• la sola folio

Adjectives usually come before the noun, just as in English. However, Esperanto word order is more flexible than English, so you may also see adjectives after the noun in some contexts:

• la folio sola

That can sound more marked, poetic, or contrastive depending on context. For a basic sentence, la sola folio is the normal choice.

Yes, Esperanto allows more flexible word order than English, because endings show grammatical roles clearly.

The normal, neutral order is:

• La sola folio velkas.

But other orders are possible for emphasis, such as:

• Velkas la sola folio.

That might sound more literary or emphatic, like Wilting is the only leaf or The only leaf is wilting with special focus.

For learners, it is best to treat subject + verb as the standard pattern unless you have a reason to emphasize something.

Both the noun and the adjective would become plural:

• La solaj folioj velkas.

Breakdown:

• folio → folioj
• sola → solaj

The verb stays the same:

• velkas

That is another important Esperanto rule: verbs do not change for singular vs. plural.

So:

• La sola folio velkas.
• La solaj folioj velkas.

Only the noun and adjective change, not the verb.