Metu po unu kovrilon sur ĉiun kaserolon.

Metu is the volitive form of meti, meaning something like a command or instruction: put, place, or set.

Esperanto uses the -u ending for commands, requests, wishes, and similar meanings. So:

• meti = to put
• metu = put / place

This form does not show whether you are talking to one person or more than one person. It can mean put to one person, put to several people, or even a polite instruction in general.

Po shows distribution: so many for each one.

In this sentence, po unu means one each or one apiece. So the idea is not just that lids are being placed, but that each casserole gets one lid.

That is the key job of po:

• unu kovrilon = one lid
• po unu kovrilon = one lid for each item in the set

Because po unu makes the distributive meaning explicit.

If you said only Metu unu kovrilon sur ĉiun kaserolon, that could sound strange, because unu kovrilon is just one lid, while sur ĉiun kaserolon refers to every casserole. Esperanto uses po to show that the one is repeated for each casserole.

So:

• unu = one
• po unu = one for each

In natural English, this is the difference between:

• put one lid and
• put one lid on each casserole

The -n marks the direct object.

The verb meti takes an object: you put something. Here, the thing being put is po unu kovrilon.

So kovrilon has -n because it is what is being placed.

Even though po is present, the noun can still take the accusative when the whole po phrase functions as the object of the verb.

Because unu means one, and a singular number normally goes with a singular noun.

So:

• unu kovrilo = one lid
• du kovriloj = two lids

Here the meaning is one lid each, so each casserole gets a single lid. Even if many lids are involved overall, the distributed unit is still one lid, so singular kovrilon is correct.

They both take -n for the same reason: sur can use the accusative to show movement toward a surface.

There is an important difference in Esperanto:

• sur la tablo = on the table, already there
• sur la tablon = onto the table, movement to that place

Since meti is a verb of placing, the sentence is talking about moving the lid onto each casserole. So sur ĉiun kaserolon means onto each casserole.

Also, ĉiun must agree with kaserolon, so both are singular and accusative.

Ĉiun means each or every, depending on how you translate it into English.

It comes from ĉiu, which refers to every member of a group one by one.

So:

• ĉiu kaserolo = each casserole / every casserole
• ĉiun kaserolon = each casserole / every casserole, with accusative

In this sentence, English would most naturally say each casserole.

Not as naturally in this context.

• sur ĉiu kaserolo would suggest location: on each casserole
• sur ĉiun kaserolon shows direction: onto each casserole

Because meti means placing something somewhere, Esperanto normally prefers the directional form here. The accusative after sur makes it clear that the lids are being moved onto the casseroles.

No. They are different words.

• po = distributive, each / apiece / at the rate of
• por = for, showing purpose, recipient, or intended use

So in this sentence, po is correct because the meaning is distributive: one lid for each casserole in the sense of one apiece.

If you used por, it would express a different relationship and would not give the same neat one each meaning.

It breaks down like this:

• Metu = put
• po unu kovrilon = one lid each
• sur ĉiun kaserolon = onto each casserole

So the structure is:

command + thing being placed + destination

That makes the whole sentence a very typical Esperanto instruction sentence.