La copa está en la mesa del comedor.

Spanish uses estar to talk about location.

• La copa está en la mesa del comedor.
  = The glass is on the dining room table (location → use estar)

Ser (es) is used for more permanent characteristics or identity:

• La copa es de cristal. = The glass is (made) of crystal.
• La mesa es grande. = The table is big.

For where something or someone is, you almost always use estar, not ser.

In Spanish, en can mean in, on, or at, depending on context.

• en la mesa = on the table
• en la caja = in the box
• en la escuela = at school

So La copa está en la mesa is the normal way to say The glass is on the table.
If you really want to emphasize “on top of,” you can use sobre or encima de:

• La copa está sobre la mesa.
• La copa está encima de la mesa.

All three (en / sobre / encima de) are fine here; en is the most common and neutral.

In Spanish, singular countable nouns almost always need some kind of determiner: an article (el, la, un, una), a demonstrative (este, esa), a possessive (mi, tu, su), etc.

So:

• La copa está en la mesa. ✅
• Copa está en mesa. ❌ (sounds wrong/unfinished)

We use la because we are talking about a specific, known cup/glass, not just any cup:

• La copa = the glass (that we both know about)
• Una copa = a glass / some glass (not specific)

In Latin American Spanish:

• copa

  • Usually: a stemmed glass, like a wine glass or champagne glass.
  • Also: a trophy (like a sports cup).
  • Example: Quiero una copa de vino. = I want a glass of wine.

• vaso

  • A tumbler or regular drinking glass (no stem), for water, juice, soda, etc.
  • Example: Quiero un vaso de agua. = I want a glass of water.

So in La copa está en la mesa del comedor, we imagine a stemmed glass, probably for wine or something similar, not a regular water glass.

Del is just the contraction of de + el:

• de
  • el → del

You must contract them when el is the masculine singular article (the):

• la mesa del comedor = the table of the dining room / the dining room table
• el libro del profesor = the teacher’s book

You do not contract if él is the pronoun (he or him):

• Hablo de él. = I talk about him. (no contraction)

Literally, la mesa del comedor means:

• la mesa = the table
• de = of
• el comedor = the dining room

So word-for-word: “the table of the dining room.”
In natural English, we would usually say “the dining room table.”

Spanish often uses noun + de + noun where English uses a compound noun or “of”:

• la puerta del baño = the bathroom door
• la mesa del comedor = the dining room table

You can say it, but it’s slightly different in nuance.

• La copa está en la mesa del comedor.
  → Think: on the dining room table (that’s the type of table; it belongs to or is associated with the dining room).

• La copa está en la mesa en el comedor.
  → Think: on the table in the dining room (you’re specifying the location step by step: on a table, which happens to be in the dining room).

Both are grammatically correct, but:

• …en la mesa del comedor is more natural if there is a “dining room table.”
• …en la mesa en el comedor might be used if there are many tables and you’re clarifying which one (the one that is in the dining room).

Spanish noun gender is partly predictable but often must be memorized.

Rough patterns (with many exceptions):

• Nouns ending in -a are usually feminine:
  • la copa
  • la mesa
• Nouns ending in -o or -or are usually masculine:
  • el comedor

So:

• la copa (fem.)
• la mesa (fem.)
• el comedor (masc.) → therefore del comedor (de + el)

You generally need to learn each noun together with its article: la mesa, el comedor, etc.

The accent mark changes both meaning and pronunciation:

• está (with accent)

  • Verb: estar, 3rd person singular present.
  • Meaning: is (temporary state/location).
  • Example: La copa está en la mesa.

• esta (no accent)

  • Demonstrative adjective/pronoun: this (feminine).
  • Example: Esta copa está en la mesa. = This glass is on the table.

So in your sentence, you must write está with an accent, because it’s the verb.

You would use hay and an indefinite article:

• Hay una copa en la mesa del comedor.
  = There is a glass on the dining room table.

Difference:

• La copa está en la mesa del comedor.
  → We both know which glass. We’re saying where that specific glass is.

• Hay una copa en la mesa del comedor.
  → We’re introducing the existence of “a glass” there, not a specific one we already had in mind.

Both are possible here:

• La copa está en la mesa del comedor.
• La copa está sobre la mesa del comedor.

Subtle difference:

• en = very general: in/on/at. Extremely common.
• sobre = more specifically on top of / over.

In practice, in Latin America, en la mesa is the most usual way to say “on the table.”
You might choose sobre if you want to stress “on top of” or sound a bit more formal or precise, but it’s not required.

Yes, it’s perfectly natural and correct.

A few notes on how it might vary in real life:

• If the context is obvious, people might just say:
  • La copa está en la mesa. (everyone already knows which room)
• Or if they’re clarifying location in the house:
  • La copa está en el comedor, en la mesa.

But your sentence La copa está en la mesa del comedor is common, clear, and natural in Latin American Spanish.

Comedor mainly means:

1. Dining room in a house or apartment:

   • Estamos en el comedor. = We are in the dining room.

2. A place where people eat in institutions or workplaces:

   • el comedor escolar = the school cafeteria
   • el comedor de la empresa = the company cafeteria

In your sentence, la mesa del comedor is clearly the dining room table in someone’s home.