El plazo de devolución termina mañana.

Plazo means a time limit, period, or deadline window for doing something. In this sentence, el plazo de devolución is the allowed period for returning something.

Fecha límite is closer to final date or deadline. In many situations, they overlap, but they are not always identical:

• plazo = the allowed period of time
• fecha límite = the specific final date

So El plazo de devolución termina mañana suggests that the return period ends tomorrow.

De devolución means for return / of return.

Here, devolución is a noun meaning return (for example, returning a product, book, or item). Spanish often uses de + noun where English might use an adjective or a different structure.

So:

• plazo de devolución = return period
• literally: period of return

This is very natural in Spanish.

Devolución is the noun form of the verb devolver.

• devolver = to return, to give back
• devolución = return, giving back

This is a common pattern in Spanish:

• verb: devolver
• noun: devolución

Examples:

• Tengo que devolver el libro. = I have to return the book.
• La devolución termina mañana. = The return period/process ends tomorrow.
  (Though el plazo de devolución is more precise here.)

Spanish often uses the present tense to talk about scheduled or very near future events, especially when there is a time expression like mañana.

So:

• termina mañana = ends tomorrow
• terminará mañana = will end tomorrow

Both can be correct, but termina mañana sounds very natural and common.

This works like English in sentences such as:

• The course starts tomorrow.
• The shop closes at six.

Yes, mañana can mean:

• tomorrow
• morning

In this sentence, it means tomorrow because of the context:

• termina mañana = it ends tomorrow

If it meant in the morning, the sentence would usually need more context, and often you would see something like:

• termina por la mañana = it ends in the morning

So here, mañana clearly means tomorrow.

Spanish usually uses a definite article more often than English does.

• el plazo = the deadline / the period
• el plazo de devolución = the return period

Even if English might say something like Return period ends tomorrow in a notice, Spanish normally prefers the article:

• El plazo de devolución termina mañana.

That sounds complete and natural.

Because plazo is a masculine noun, so it takes:

• el plazo

There is no special rule here that makes it obvious from meaning alone; you generally learn the noun together with its article:

• el plazo
• la devolución

Notice that in this sentence, the main noun is plazo, so the article agrees with plazo, not with devolución.

Because the subject is singular:

• El plazo de devolución = the return period

The whole phrase is singular because the main noun is plazo.

So the verb must also be singular:

• El plazo ... termina

If it were plural, you would get:

• Los plazos de devolución terminan mañana.
  = The return periods end tomorrow.

Yes, often you can.

• termina mañana
• acaba mañana

Both can mean ends tomorrow.

However, terminar is often a very straightforward, neutral choice in formal notices or administrative language. Acabar is also common, but terminar may sound slightly more standard here.

So El plazo de devolución termina mañana is a very natural choice, especially in formal or written contexts.

Yes, you can also say:

• Mañana termina el plazo de devolución.

That is completely correct.

The difference is mainly emphasis:

• El plazo de devolución termina mañana.
  Focuses first on the return period
• Mañana termina el plazo de devolución.
  Emphasises tomorrow

Spanish word order is more flexible than English, although the original version is probably the most neutral.

Yes, it sounds natural and standard in Spain.

It would fit well in contexts like:

• a shop return policy
• a library notice
• an online order return window
• official information

It has a slightly formal or informational tone, which is exactly what you would expect for this kind of message.

A simple pronunciation guide is:

el PLA-tho de deh-boh-loo-THYON ter-MEE-na ma-NYA-na

In most of Spain:

• z in plazo sounds like th in think
• c before i/e also often has that th sound
• ll and y vary by speaker, but that does not affect this sentence
• ñ in mañana sounds like ny in canyon

A rough breakdown:

• El
• plazo
• de
• devolución
• termina
• mañana

The stress falls on:

• PLA-zo
• devo-lu-CIÓN
• ter-MI-na
• ma-ÑA-na