Learn Hardcore Spanish (Latin America): Mi profesor escribe en el foro que hay que participar cada semana. - My teacher writes in the forum that you must participate every week.

Hay que + infinitive expresses a general obligation or necessity, like English “one must …” or “it’s necessary to …”, without saying who exactly has to do it.

Hay que participar cada semana.
≈ One must participate every week / It’s necessary to participate every week.

Tenemos que + infinitive attaches the obligation to “we”:

Tenemos que participar cada semana.
≈ We have to participate every week.

So in your sentence, hay que participar cada semana sounds like a general rule for everyone in the class, not just “we.” It’s more impersonal and rule-like, as if it’s the course policy.

What is the role of que in escribe en el foro que hay que participar…?

Here que is the conjunction “that”, introducing a subordinate clause:

Main clause: Mi profesor escribe en el foro
(My teacher writes in the forum)
Subordinate clause introduced by que: que hay que participar cada semana
(that you/one must participate every week)

Together they mean: “My teacher writes in the forum that you have to participate every week.”

In English we can drop “that”:
My teacher writes in the forum (that) you have to participate every week.
In Spanish, que is usually kept in, especially in writing.

Why is it hay que participar and not something like participamos or participen?

Because the structure hay que + infinitive is fixed:

Hay que participar
literally: There is that to participate → One must participate.

Spanish uses the infinitive after hay que, never a conjugated verb:

✅ Hay que estudiar. (You/one must study.)
❌ Hay que estudiamos.
❌ Hay que estudien.

If you wanted to say “We have to participate”, you would switch constructions:

Tenemos que participar. (We have to participate.)
still with participar in the infinitive.

Why is escribe in the present tense here? Would escribió (past) also work?

Escribe (present) is used because the sentence describes something that:

is a regular action (he does this as a rule), or
is current/recent enough to be seen as “now” (for example, something he has posted in the forum that you can see).

Spanish present tense often covers:

current actions
general truths
habitual actions

Mi profesor escribe en el foro que hay que participar cada semana suggests this is something he writes (or has written as a standing rule).

You could say:

Mi profesor escribió en el foro que hay que participar cada semana.
This focuses more on a specific past action: He wrote (at some point) in the forum that you must participate every week.

Why is it en el foro and not al foro or por el foro?

The preposition en usually corresponds to “in / on / at” for location.

Escribe en el foro
= He writes in the forum (i.e., he posts inside that online space).

Other prepositions would change the meaning:

al foro = to the forum (direction/destination, not where he writes)
por el foro = through the forum / around the forum (movement or distribution, not the place where the writing appears)

So en el foro is the natural choice for where he is writing (where the message appears).

Why is it el foro with el? Could we just say escribe en foro?

In Spanish, you normally need an article (or another determiner) with singular countable nouns, unless it’s a title, list, or very special context.

✅ en el foro (in the forum)
❌ en foro (this sounds incomplete/wrong in normal sentences)

So el is required here. If you wanted to be more specific, you could say:

en el foro de la clase – in the class forum
en nuestro foro – in our forum

Can the word order change? For example, can I say Mi profesor escribe que hay que participar cada semana en el foro?

Yes, that’s grammatically fine, and very natural in Spanish. Word order is somewhat flexible.

Original:

Mi profesor escribe en el foro que hay que participar cada semana.
Slight emphasis on where he writes (in the forum).

Alternative:

Mi profesor escribe que hay que participar cada semana en el foro.
Slight emphasis on where you must participate (in the forum every week).

Context decides which is clearer:

If the rule is “you must participate in the forum every week,” the second order can make that link a bit clearer.
If you’re focusing on the fact that he writes this in the forum (as opposed to saying it in class), the original is also very natural.

Both are correct and common.

What’s the difference between cada semana and todas las semanas?

Both mean “every week”, and in most contexts they’re interchangeable.

cada semana – literally “each week”
todas las semanas – literally “all the weeks”

Subtle nuance (often very slight):

cada semana can sound a bit more neutral or rule-like:
Hay que participar cada semana. – You must participate each week.
todas las semanas might feel a bit more like emphasizing frequency or repetition:
Participo en el foro todas las semanas. – I participate in the forum every single week.

In everyday speech, you can use either here: cada semana or todas las semanas.

Why is there no subject pronoun él before escribe?

In Spanish, subject pronouns (yo, tú, él, etc.) are usually dropped because the verb ending already shows who the subject is.

(Él) escribe – he writes
(Ella) escribe – she writes
(Yo) escribo – I write

In Mi profesor escribe en el foro…, mi profesor is the subject, so adding él would be redundant:

❌ Mi profesor él escribe en el foro… (incorrect / sounds wrong)
✅ Mi profesor escribe en el foro… (correct)

How would the sentence change if the teacher is a woman?

Only the noun for “teacher” needs to change to the feminine form:

Mi profesora escribe en el foro que hay que participar cada semana.

Everything else (verb forms, hay que, etc.) stays the same, because Spanish verbs do not change for gender, only for person/number.

Could you replace hay que with tenemos que here? Would it change the meaning?

Yes, you could say:

Mi profesor escribe en el foro que tenemos que participar cada semana.

Meaning change:

que hay que participar cada semana
= that one must participate every week / that it’s necessary to participate every week (general, impersonal rule)
que tenemos que participar cada semana
= that we have to participate every week (the obligation falls specifically on “us”)

So with tenemos que, the teacher is explicitly saying we (probably the class) must participate.

Is hay que always followed by an infinitive?

Yes. The structure is:

hay que + infinitive

Examples:

Hay que leer el capítulo. – You/one must read the chapter.
Hay que llegar temprano. – You/one must arrive early.
Hay que participar cada semana. – You/one must participate every week.

You do not conjugate the verb after hay que:

❌ Hay que llegamos temprano.
✅ Hay que llegar temprano.

Could the part que hay que participar cada semana ever use the subjunctive?

No, not with hay que. The pattern hay que + infinitive is fixed; it does not trigger the subjunctive because the verb stays in the infinitive form:

que hay que participar (infinitive)
not que haya que participemos, etc.

You do see subjunctive after some expressions of obligation, but with different structures:

Es necesario que participemos cada semana.
(It’s necessary that we participate every week. → participemos, subjunctive)
Mi profesor exige que participemos cada semana.
(My teacher demands that we participate every week. → participemos, subjunctive)

With hay que, it always stays: hay que + infinitive.

How do you pronounce the tricky words in this sentence?

Key words with approximate English-like guidance (Latin American pronunciation):

profesor → pro-fe-SOR
- Stress on the last syllable: pro-fe-SOR.
escribe → es-CRI-be
- Stress on CRI: es-KREE-beh.
foro → FO-ro
- Stress on FO: FO-roh.
participar → par-ti-si-PAR
- Stress on PAR: par-tee-see-PAR.
semana → se-MA-na
- Stress on MA: seh-MA-na.

Remember that in Spanish:

e = like “e” in get (but a bit clearer)
a = like “a” in father
i = like “ee” in see
o = like “o” in go (but shorter)