Learn Hardcore Spanish (Spain): En esa clase hay personas jóvenes y adultas que estudian la misma asignatura. - In that class there are young people and adults who study the same subject.

Hay (from haber) is used to say that something exists or that there is/are something in a place, without identifying or describing a specific known thing.

En esa clase hay personas… = In that class there are people… (introducing their existence)
Son personas jóvenes = They are young people (describing people already identified)
Están en la clase = They are in the class (their location/state)

So the sentence starts by introducing the existence of some people in that class, so Spanish uses hay.

What does hay literally mean, and how is it pronounced?

Hay means both “there is” and “there are” in the present tense. It does not change for singular or plural:

Hay una persona. = There is one person.
Hay muchas personas. = There are many people.

Pronunciation: /ai/, like English “eye”.
The h is silent: hay sounds the same as the interjection ay (as in “ouch!”).

Why is it esa clase and not ese clase or aquel clase?

Because clase is a feminine noun in Spanish.

Demonstratives agree in gender and number with the noun:

este / esta / estos / estas (this / these, near the speaker)
ese / esa / esos / esas (that / those, a bit farther or not so close)
aquel / aquella / aquellos / aquellas (that / those, far away or more “distant”)

Since clase is feminine singular, you must use the feminine form:

✅ esa clase
❌ ese clase (masculine with feminine noun – wrong)
aquel clase is also wrong for the same reason; it would have to be aquella clase if you wanted to say that class (over there / more distant).

What is the difference between esa clase and esta clase?

Both mean “that/this class”, but they signal different “distance”:

esta clase = this class (close to the speaker in space, time, or context; often the one you are in right now or are just talking about as “this one”).
esa clase = that class (a bit farther away, or not the one you’re directly involved in at the moment; maybe one you’re referring to but not inside).

So:

En esta clase hay personas… → in this class (probably the one we’re in now)
En esa clase hay personas… → in that class (another one; not “ours”)

Why are jóvenes and adultas placed after personas, not before?

In Spanish, descriptive adjectives (colors, age, size, etc.) usually come after the noun:

personas jóvenes = young people
personas adultas = adult people

Putting them before the noun is possible but often sounds more literary or gives a more subjective or emphatic nuance. The neutral, standard word order is:

noun + adjective → personas jóvenes, clase difícil, libro interesante

Why is it personas jóvenes y adultas and not personas jóvenes y adultos?

Because personas is a feminine plural noun, and in Spanish adjectives must agree in gender and number with the noun they modify.

Here, both adjectives refer to personas:

personas jóvenes → jóvenes = plural (valid for both genders)
personas adultas → adultas = feminine plural, matching personas

So you need:

✅ personas jóvenes y adultas

Using adultos would be masculine plural and would not agree with personas:

❌ personas jóvenes y adultos (ungrammatical, mismatched agreement)

Does personas jóvenes y adultas mean that each person is both young and adult at the same time?

No. In context, personas jóvenes y adultas is naturally understood as two groups of people:

some are jóvenes (young)
some are adultas (adult)

Spanish often uses this pattern:

niños y adultos = children and adults
alumnos nuevos y antiguos = new and old students

If you wanted to make the split even clearer, you could say:

personas tanto jóvenes como adultas
personas, unas jóvenes y otras adultas

But the original is normally read as “young people and adults” in one class.

Could you say gente joven y adulta instead of personas jóvenes y adultas?

Yes, you could say:

En esa clase hay gente joven y adulta que estudia la misma asignatura.

Differences:

gente = “people” as a collective, grammatically singular and usually feminine:
- La gente es simpática. (not son simpáticas)
personas = “persons / people” as countable individuals, grammatically plural:
- Las personas son simpáticas.

So:

personas jóvenes y adultas → emphasizes individual people.
gente joven y adulta → emphasizes the group as a whole.

Both are fine; personas is a bit more formal/precise.

Why is the relative pronoun que used to mean “who” here? Could I use quienes?

In Spanish, que is the most common relative pronoun and can mean who / that / which depending on context. It works for people, things, and animals:

personas que estudian… = people who study…

You can use quienes for people:

personas que estudian la misma asignatura
personas que estudian la misma asignatura, quienes son muy dedicadas.

Differences:

que is more frequent and more neutral, used in almost all registers.
quienes is more formal and is used only for people, often when the pronoun has its own preposition or in more elaborate sentences.

In the original sentence, que is the most natural choice.

Why is it la misma asignatura and not las mismas asignaturas?

Because the idea is: they all study one single subject in common.

la misma asignatura = the same subject (one subject shared by all)
las mismas asignaturas = the same subjects (several subjects, and each person has the same set)

So:

En esa clase hay personas… que estudian la misma asignatura.
→ They all study one identical subject (e.g. “Biology 101”).

If you wanted to say they all have exactly the same list of courses, you’d say:

…que estudian las mismas asignaturas.

What is the difference between misma and igual in this context?

Both can be related to “same,” but they are not interchangeable here:

la misma asignatura = the same subject, identical, literally the same course.
una asignatura igual = a similar subject, a subject that is alike in some way, not necessarily the identical course.

Examples:

Estudian la misma asignatura.
→ They study the very same course (e.g. all in the same Spanish 101 group).
Estudian asignaturas iguales.
→ They study subjects that are similar (maybe different universities, but comparable courses).

In this sentence, you need la misma asignatura to express strict identity.

What does asignatura mean exactly, and how is it different from materia or sujeto?

In Spain:

asignatura = a school / university subject or course, like Matemáticas, Historia, Biología.
- Mi asignatura favorita es Historia.
materia = subject matter / field, more general, also used for school subjects, but often in a slightly more technical or broad sense:
- materias del Bachillerato (subjects in high school)
- la materia de estudio (the matter/subject being studied)
sujeto almost never means an academic subject. Instead:
- grammar: the subject of a sentence → el sujeto de la oración
- person as an individual (sometimes slightly negative or neutral) → un sujeto extraño = a strange guy

So in European Spanish, asignatura is the natural word here for school subject.

Can I drop the article and say estudian misma asignatura?

No. In this case, the article la is required:

✅ estudian la misma asignatura
❌ estudian misma asignatura

In Spanish, common nouns (like asignatura) usually need a definite or indefinite article when they’re specific:

Estudian la misma asignatura.
Estudian una asignatura muy difícil.

You can sometimes drop the article with proper names of fields (e.g. Estudia Medicina, Historia, Derecho), but asignatura is not a proper name; it’s a common noun, so la is needed here.