Mi legas la recenzon.

Because recenzon has the ending -n, which marks the direct object in Esperanto.

In this sentence:

• Mi = I
• legas = read / am reading
• la recenzon = the review

The review is the thing being read, so it takes -n.

A useful contrast:

• recenzo = a review / review as a basic noun form
• recenzon = a review / the review as the direct object

This is called the accusative ending.

The ending -as shows the present tense.

So legas means:

• read
• am reading
• is reading
  depending on context

Esperanto uses one present-tense ending, -as, for all subjects:

• mi legas = I read / I am reading
• vi legas = you read / you are reading
• li legas = he reads / he is reading

The verb form does not change for different persons.

Because Esperanto verbs do not agree with the subject in person or number.

In English, we say:

• I read
• he reads

But in Esperanto, the verb stays the same:

• mi legas
• li legas
• ili legas

This makes verb conjugation much simpler. The tense ending matters, but the subject does not change the verb form.

La means the.

It is the Esperanto definite article, and it is completely invariable. That means it never changes:

• not for singular or plural
• not for subject or object
• not for gender

So you get:

• la recenzo = the review
• la recenzon = the review
• la recenzoj = the reviews
• la recenzojn = the reviews

Notice that la always stays la.

Usually, no. In normal Esperanto, you normally include the subject pronoun.

That is because the verb ending tells you the tense, but not the person:

• legas only tells you it is present tense
• it does not tell you whether the subject is I, you, he, she, they, etc.

So Mi legas is the normal way to say I am reading. If you only said Legas, the listener would usually not know who is doing the action.

Mi legas la recenzon is the most normal word order: subject – verb – object.

But Esperanto word order is fairly flexible because the -n on recenzon shows that it is the object.

So these can still be understood:

• La recenzon mi legas.
• Legas mi la recenzon.

However, these different orders may sound marked, poetic, or emphatic. For a learner, the safest and most natural order is:

Mi legas la recenzon.

It can mean either, depending on context.

Esperanto present tense often covers both:

• I read
• I am reading

So Mi legas la recenzon could mean:

• I read the review
• I am reading the review

If the context makes the timing clear, Esperanto usually does not need a separate progressive form like English am reading.

Esperanto has no indefinite article. There is no separate word for a or an.

So:

• recenzo can mean a review or just review
• la recenzo means the review

In this sentence, la is used, so it specifically means the review.

The ending -o tells you that recenzo is a noun.

In Esperanto, word endings are very regular:

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

So from recenzo, you can immediately see that it is a noun. Then recenzon is the same noun with the direct-object ending -n added.

A simple pronunciation guide is:

re-CEN-zon

A few helpful points:

• the stress is on the second-to-last syllable
• c is pronounced like ts
• z is pronounced like English z

So recenzon sounds roughly like:

reh-TSEN-zon

And the full sentence:

Mi legas la recenzon
roughly: mee LEH-gahs lah reh-TSEN-zon

Yes. In Esperanto, adjectives agree with the nouns they describe in both number and case.

So if you had an adjective with recenzon, it would also take -n:

• la interesa recenzo = the interesting review
• mi legas la interesan recenzon = I am reading the interesting review

Here:

• interesa matches the noun as an adjective
• interesan gets -n because recenzon is the direct object

This agreement is an important feature of Esperanto grammar.