Learn Hardcore Spanish (Latin America): Mi profesor dice que cada equivocación es una oportunidad para aprender. - My teacher says that every mistake is an opportunity to learn.

The possessive (mi, tu, su, nuestro, etc.) already shows that we are talking about a specific person, so adding el / la is not needed and sounds wrong in this context.

How would the sentence change if the teacher is a woman? Do I just change profesor to profesora?

Yes. You change the noun to the feminine form:

Mi profesor dice que… = My (male) teacher says that…
Mi profesora dice que… = My (female) teacher says that…

Nothing else in the sentence needs to change, because profesor / profesora doesn’t affect the rest of the words here.

Why do we need que after dice? In English we can often drop that in “My teacher says (that) every mistake…”.

In Spanish, you must keep the conjunction que in this type of sentence.

Mi profesor dice que… = My teacher says that…

The structure is:

[main clause] Mi profesor dice
que
(that)
[subordinate clause] cada equivocación es una oportunidad para aprender.

In everyday English, that can be omitted. In Spanish, you can’t omit que here:

Mi profesor dice cada equivocación es… ❌ (incorrect)

Could we say Mi profesor dijo que… instead of dice que? What’s the difference?

Yes, you can, but the meaning in time changes:

Mi profesor dice que…
- Present tense (dice)
- Suggests he says this regularly, or is saying it now.
Mi profesor dijo que…
- Simple past (dijo)
- Refers to something he said at a specific time in the past.

So you choose dice or dijo depending on whether you want a general, current habit (dice) or a past event (dijo).

Why is it cada equivocación (singular) and not cada equivocaciones (plural)?

In Spanish, cada is always followed by a singular noun, even though the idea is “each one of many”.

cada equivocación ✅ (each mistake)
cada día ✅ (every day)
cada equivocaciones ❌

If you want to use the plural noun, you switch to a different determiner:

todas las equivocaciones = all the mistakes
las equivocaciones = the mistakes

What’s the difference between equivocación and error? Could we say cada error instead?

Both are often translated as mistake, but they have slightly different flavors:

equivocación
- Very common in everyday language.
- Emphasizes the act of being wrong / making a mistake, often in a softer or more human way.
- Fits very well with motivational phrases like this one.
error
- A bit more neutral or technical.
- Used a lot in academic, formal, or technical contexts (errores gramaticales, errores de cálculo).

You could say:

Mi profesor dice que cada error es una oportunidad para aprender.

That’s correct and natural. The original with equivocación just sounds a little warmer and more personal.

Why do we use es and not sea (subjunctive) after dice que?

After dice que, you usually use:

Indicative (like es) when you’re stating something presented as a fact or general truth.
Subjunctive (like sea) when expressing doubt, desire, unreality, emotion, etc.

Here the teacher is affirming a general principle:

cada equivocación es una oportunidad para aprender
(each mistake is an opportunity to learn)

This is treated as a statement of belief/fact, so es (indicative) is the natural choice.

Examples where you would use subjunctive:

Mi profesor quiere que cada equivocación sea una oportunidad para aprender.
(My teacher wants each mistake to be an opportunity to learn.)

Here it’s not a stated fact; it’s a wish, so sea is used.

Why is it oportunidad para aprender and not oportunidad de aprender? Are both possible?

Both oportunidad para + infinitive and oportunidad de + infinitive are used in Spanish. In this sentence:

oportunidad para aprender sounds very natural and common, especially in motivational or didactic phrases.
oportunidad de aprender is also correct and common.

Nuance (often very subtle and context‑dependent):

para + infinitive tends to highlight purpose or goal:
- una oportunidad para crecer (an opportunity in order to grow)
de + infinitive can sound a bit more neutral / descriptive:
- tuvimos la oportunidad de crecer (we had the opportunity to grow)

In practice, both are fine here, and many speakers wouldn’t feel any difference.

Why is aprender in the infinitive? Why not conjugate it, like aprendemos?

In Spanish, after para to express purpose, you normally use the infinitive:

para aprender = in order to learn
para comer = to eat
para descansar = to rest

If you used aprendemos, the meaning and structure would change completely:

…es una oportunidad para aprendemos ❌ (incorrect grammar)
You’d need something like: …es una oportunidad y aprendemos (it’s an opportunity and we learn), which is a different sentence.

So here, para + infinitive is the correct structure to express purpose:
una oportunidad para aprender = an opportunity to learn.

Can we change the word order, like: Cada equivocación es una oportunidad para aprender, dice mi profesor?

Yes, that’s perfectly correct and very natural:

Mi profesor dice que cada equivocación es una oportunidad para aprender.
Cada equivocación es una oportunidad para aprender, dice mi profesor.

Both mean the same thing. The second version:

Emphasizes the idea more (puts it first),
Then attributes it to the teacher at the end.

This kind of word order variation is normal in Spanish, especially in written or slightly more literary / reflective styles.