Ĉiu persono ricevas unu semon.

A word-by-word breakdown:

• Ĉiu = each / every
• persono = person
• ricevas = receives / gets
• unu = one
• semon = seed as the direct object

So the structure is basically:

Each person receives one seed.

The -n marks the direct object in Esperanto.

Here, the thing being received is the seed, so semo becomes semon.

• semo = seed
• semon = seed as the object of the verb

This is very common in Esperanto:

• La knabo vidas hundon. = The boy sees a dog.
• Mi havas libron. = I have a book.

In your sentence, unu semon is the thing each person receives, so it gets -n.

In Esperanto, -as marks the present tense.

So:

• ricevas = receives / is receiving
• ricevis = received
• ricevos = will receive

One very useful feature of Esperanto is that the verb ending does not change depending on the subject:

• mi ricevas = I receive
• vi ricevas = you receive
• li ricevas = he receives
• ili ricevas = they receive

So ricevas works for ĉiu persono just as it would for any other subject.

Ĉiu persono means each person / every person and treats people one by one.

• ĉiu persono = each person, every person
• ĉiuj personoj = all people, all persons

Both can sometimes be translated similarly in English, but the feeling is a little different:

• Ĉiu persono ricevas unu semon. = Each person receives one seed.
• Ĉiuj personoj ricevas unu semon. = All the people receive one seed.

The singular form with ĉiu is very common when talking about individuals separately.

Yes—Esperanto has no indefinite article like English a/an.

So:

• semo can mean a seed or just seed, depending on context.
• unu semo means one seed specifically.

That means unu is not just an article here; it really emphasizes the number one.

Compare:

• Ĉiu persono ricevas semon. = Each person receives a seed.
• Ĉiu persono ricevas unu semon. = Each person receives one seed.

So in your sentence, unu makes the quantity explicit.

Esperanto handles articles differently from English.

• It has la = the
• It has no word for a/an

So:

• persono = person / a person
• semo = seed / a seed
• la persono = the person
• la semo = the seed

In your sentence, there is no la, so the nouns are not specifically the person or the seed. The meaning is more general.

A simple pronunciation guide:

• Ĉiu ≈ CHEE-oo
• persono ≈ per-SO-no
• ricevas ≈ ree-TSEH-vas
• unu ≈ OO-noo
• semon ≈ SEH-mon

A few useful pronunciation points:

• ĉ sounds like ch in church
• c sounds like ts in cats
• Stress usually falls on the second-to-last syllable

So the whole sentence is pronounced roughly:

CHEE-oo per-SO-no ree-TSEH-vas OO-noo SEH-mon

Yes, Esperanto word order is fairly flexible, partly because the -n shows the direct object.

The most neutral order is:

Ĉiu persono ricevas unu semon.

But other orders are possible for emphasis, for example:

• Unu semon ricevas ĉiu persono.
• Ricevas ĉiu persono unu semon.

These still mean roughly the same thing, though the emphasis changes. For learners, it is best to start with the normal subject–verb–object order.

No. Esperanto verbs do not agree with the subject in person or number.

English changes:

• I receive
• she receives

Esperanto does not:

• mi ricevas
• ŝi ricevas
• ili ricevas

So ricevas stays the same no matter who is doing the action.

This makes Esperanto grammar much simpler than English in this area.

The dictionary form is semo.

In Esperanto, nouns normally end in -o:

• semo = seed
• persono = person

When a noun is the direct object, you add -n:

• semon = seed as an object

So if you look the word up, you would look for semo, not semon.

You would make semo plural with -j, and if it is still the direct object, it also keeps -n.

So:

• semo = seed
• semoj = seeds
• semon = seed (object)
• semojn = seeds (object)

Examples:

• Ĉiu persono ricevas du semojn. = Each person receives two seeds.
• Ĉiu persono ricevas kelkajn semojn. = Each person receives several seeds.

So if the object is plural and direct, the ending becomes -jn.

Usually, yes, when it means each/every before a noun.

So you commonly get:

• ĉiu persono = each person
• ĉiu tago = every day
• ĉiu libro = each book

If you use the plural form ĉiuj, it usually refers to all members of a group:

• ĉiuj personoj = all people
• ĉiuj libroj = all books

So in this sentence, ĉiu persono is exactly the normal pattern for every person.