Pon el vaso sobre el posavasos para no manchar la mesa.

Pon is the tú affirmative imperative of poner (to put / to place).

So:

• poner = to put
• pon = put! (when speaking to one person informally)

This is an irregular command. You might expect something like pone, but the tú command is pon.

Compare:

• Pon el vaso... = Put the glass...
• Poned el vaso... = Put the glass... (to more than one person, informal in Spain)
• Ponga el vaso... = Put the glass... (formal singular)

Spanish often uses the definite article more than English does. El vaso means the glass.

In instructions like this, Spanish usually includes the article:

• Pon el vaso sobre el posavasos
  literally: Put the glass on the coaster

Even if English might sometimes say Put your glass on a coaster, Spanish commonly uses el when the object is clear from context.

Vaso usually means a drinking glass or sometimes a cup-shaped container.

In everyday use:

• vaso = drinking glass / tumbler
• copa = stemmed glass, like a wine glass
• taza = cup, usually with a handle

So in this sentence, el vaso is most naturally the glass.

Yes, here sobre means on / on top of.

So:

• sobre el posavasos = on the coaster

It suggests physical contact: the glass is placed resting on the coaster.

Spanish can also use:

• encima de = on top of

For example:

• Pon el vaso encima del posavasos

That sounds possible too, but sobre is very natural and slightly more compact in this kind of instruction.

Posavasos means coaster.

It can be confusing because it ends in -s, but the singular form is still el posavasos. The plural is also los posavasos.

This happens because the word is formed from:

• posa- from posar / poner-related idea of placing/resting
• vasos = glasses

So literally it is something like a thing for glasses to rest on, but in actual meaning it is just coaster.

Examples:

• el posavasos = the coaster
• los posavasos = the coasters

Because the glass is being placed on top of the coaster, not inside it.

• sobre = on / on top of
• en = in / on / at, depending on context

A coaster is a flat object, so Spanish normally says:

• sobre el posavasos

Using en el posavasos would sound unnatural here because a glass does not go inside a coaster.

This is a very common Spanish structure:

• para = in order to / so as to
• no = not
• manchar = to stain / to mark / to make dirty
• la mesa = the table

So:

• para no manchar la mesa = so as not to stain the table / so you don’t stain the table

After para, Spanish often uses the infinitive when the subject stays general or is understood:

• Estudio para aprender. = I study in order to learn.
• Cierra la ventana para no pasar frío. = Close the window so as not to get cold.

Because after para, Spanish often uses the infinitive.

So:

• para no manchar la mesa = in order not to stain the table

This is similar to English to stain in in order not to stain.

If Spanish used a full conjugated clause, it would need a different structure, for example:

• Pon el vaso sobre el posavasos para que no manches la mesa.

That is also possible, but it is a bit more explicit and usually less direct than the original sentence.

It can mean both, depending on context.

Common meanings:

• to stain
• to mark
• to make dirty

In this sentence, the idea is that condensation or liquid from the glass could leave a mark on the table, so stain is probably the best translation.

Examples:

• Manchaste la camisa. = You stained the shirt.
• No manches la mesa. = Don’t stain / mark up the table.

Because manchar takes a direct object directly.

• manchar la mesa = to stain the table

No preposition is needed.

Compare:

• limpiar la mesa = to clean the table
• romper el vaso = to break the glass
• manchar la mesa = to stain the table

English learners sometimes expect a preposition because English phrasing can vary, but in Spanish the object comes straight after the verb here.

Yes. That is also correct, but it changes the structure and emphasis a little.

Compare:

1. para no manchar la mesa
   = so as not to stain the table
   This is more direct and compact.

2. para que no se manche la mesa
   = so that the table doesn’t get stained
   This focuses more on the table as the thing affected.

The second version uses:

• para que
  • subjunctive
• se manche from mancharse / passive-like use

Both are natural, but the original sentence is simpler and very common in everyday instructions.

Yes, it sounds natural in Spain.

It is a normal everyday instruction. A native speaker might also say:

• Pon el vaso en el posavasos in some regions, though sobre is more precise
• Pon el vaso encima del posavasos
• Deja el vaso en el posavasos = Leave the glass on the coaster

The original sentence is clear, correct, and natural.

Both can work, but they are slightly different.

• pon = put / place
• deja = leave / set down

So:

• Pon el vaso sobre el posavasos = Put the glass on the coaster.
• Deja el vaso sobre el posavasos = Leave the glass on the coaster / Set the glass down on the coaster.

Pon focuses on the action of placing it there.
Deja can sound a little softer and more like set it there and keep it there.

More or less, yes:

• Pon = put
• el vaso = the glass
• sobre = on
• el posavasos = the coaster
• para no manchar = so as not to stain
• la mesa = the table

A very literal version is:

Put the glass on the coaster so as not to stain the table.

A more natural English translation might be:

Put the glass on the coaster so you don’t stain the table.