El cupo está lleno hoy.

In this sentence, cupo means the number of available places, spots, seats, or openings. It is very common in Latin American Spanish when talking about things like classes, appointments, events, or programs.

So el cupo está lleno hoy means that today's available spots are already taken.

Examples:

• No hay cupo para mañana. = There are no spots for tomorrow.
• Todavía quedan cupos. = There are still spots left.

Spanish uses estar here because lleno describes a current condition or state: the capacity is full today.

• estar lleno = to be full
• ser is usually not used with lleno in this kind of situation

So:

• El cupo está lleno hoy = The spots are full today.

This fits the common ser vs. estar pattern:

• ser for identity, basic characteristics, origin, etc.
• estar for states, conditions, and locations

Because availability can change from day to day, estar is the natural choice.

Because cupo is a masculine noun, so it takes the masculine article el.

• el cupo
• un cupo

This is something you generally just have to learn with the noun. The ending -o often suggests masculine nouns, and in this case that pattern is true.

Because adjectives usually agree with the noun they describe in gender and number.

Here, lleno describes cupo, which is:

• masculine
• singular

So the adjective must also be:

• masculine
• singular

That gives us lleno.

Compare:

• El cupo está lleno.
• La sala está llena.
• Los cupos están llenos.
• Las salas están llenas.

Yes, hoy can move around. Spanish word order is flexible, especially with time expressions.

All of these are possible:

• El cupo está lleno hoy.
• Hoy el cupo está lleno.
• El cupo hoy está lleno.

The most natural choice depends on what you want to emphasize:

• El cupo está lleno hoy. = neutral
• Hoy el cupo está lleno. = emphasizes today

Putting hoy at the end is very normal.

Yes. In many Latin American countries, cupo is a very common word for available space or capacity in things like:

• courses
• appointments
• government programs
• events
• reservations

Depending on the country and situation, you may also hear:

• lugar
• espacio
• vacante
• plaza

For example:

• Ya no hay cupos.
• No quedan lugares.
• No hay vacantes.

They are similar, but cupo is especially common in institutional or administrative contexts.

Yes, and those are very common alternatives.

There is a small nuance:

• El cupo está lleno hoy focuses on the capacity being full.
• No hay cupo hoy focuses on there being no availability.
• Ya no hay cupo adds the idea of no longer being available.

Examples:

• No hay cupo hoy. = There is no availability today.
• Ya no hay cupo para la clase. = There is no more room in the class.
• El cupo está lleno. = The capacity is full.

All are natural, but no hay cupo is often especially common in everyday use.

Yes.

Singular cupo can refer to available capacity in a general sense:

• No hay cupo.

Plural cupos refers to multiple spots or openings:

• Hay dos cupos disponibles.
• Se acabaron los cupos.

So:

• cupo = availability / room / one slot
• cupos = spots / openings

Both are very common.

It literally means full, but in context it often works like fully booked, sold out, or no more spots available.

So in practical English, depending on the situation, this sentence could correspond to:

• It’s full today.
• It’s fully booked today.
• There are no spots left today.

Spanish often uses lleno in a wider, more flexible way than English full.

It is neutral and works in both formal and informal situations.

You could hear or read it:

• at a clinic
• in a school
• in customer service
• in casual conversation

If you want a more formal or institutional style, you might also see:

• No hay cupo disponible hoy.
• El cupo para hoy está completo.

But El cupo está lleno hoy is perfectly normal and understandable.