Learn Hardcore Romanian: Profesoara explică de ce greșeala este interesantă pentru toți elevii. - The female teacher explains why the mistake is interesting for all the students.

In the sentence, Profesoara already means “the (female) teacher”.
It’s capitalized only because it’s at the beginning of the sentence, not because it’s a name.

What is the difference between profesor, profesoară, and profesoara?

They differ in gender and definiteness:

profesor – male teacher, indefinite or generic
- un profesor = a (male) teacher
- profesorul = the (male) teacher
profesoară – female teacher, indefinite
- o profesoară = a (female) teacher
profesoara – the female teacher, definite
- profesoara = the (female) teacher

In your sentence, Profesoara refers to a specific female teacher: “The (female) teacher explains…”.

Does explică mean “explains” or “is explaining”? How do I know?

Romanian only has one present tense form here: (ea) explică.

This single form can correspond to both:

“The teacher explains…” (habitual / general statement)
“The teacher is explaining…” (right now)

Context normally decides:

For a general statement: Profesoara explică mereu foarte bine. – The teacher always explains very well.
For something happening now: Profesoara explică acum lecția. – The teacher is explaining the lesson now.

In your sentence, Profesoara explică de ce…, both translations are possible depending on the wider context.

Why do we use de ce here and not something like că (“that”)?

In English, you say: “The teacher explains why the mistake is interesting.”
The word “why” introduces an indirect question. Romanian does the same:

de ce = why

So:

Profesoara explică de ce greșeala este interesantă…
= The teacher explains why the mistake is interesting…

If you used că, it would change the meaning:

Profesoara explică că greșeala este interesantă.
= The teacher explains that the mistake is interesting. (a statement, not a “why” question)

So de ce is needed because the teacher is explaining the reason (why), not just stating a fact.

In de ce greșeala este interesantă, why is the order “greșeala este” and not “este greșeala” like in a question?

Good observation: Romanian distinguishes between direct and indirect questions with word order.

Direct question (you are actually asking):
De ce este greșeala interesantă? – Why is the mistake interesting?
(verb este comes before the subject greșeala)
Indirect question (embedded inside another sentence, like after “explain why”):
Profesoara explică de ce greșeala este interesantă.
– The teacher explains why the mistake is interesting.
(normal statement order: subject + verb → greșeala este)

So:

Direct question: De ce este greșeala interesantă?
Indirect question: Profesoara explică de ce greșeala este interesantă.

What’s the difference between greșeală and greșeala?

The difference is again the definite article:

greșeală – a mistake (indefinite form)
- o greșeală = a mistake
greșeala – the mistake (definite form, article attached)
- greșeala = the mistake

In your sentence:

greșeala este interesantă = the mistake is interesting.

So greșeala already contains the meaning of “the mistake”.

Why is the adjective interesantă after the noun greșeala, and why does it end in -ă?

Two things are happening:

Position
In Romanian, adjectives usually follow the noun:
- greșeala interesantă – the interesting mistake
  This is the normal order.
Agreement
Adjectives must agree in gender and number with the noun:
- greșeală is feminine singular.
- So the adjective must also be feminine singular: interesantă.

Basic forms of the adjective interesant (“interesting”):

Masculine singular: interesant
Feminine singular: interesantă
Masculine plural: interesanți
Feminine plural: interesante

Since greșeala is feminine singular, we say:

greșeala este interesantă, not interesant.

Could we say Greșeala este interesantă pentru toți elevii without Profesoara explică?

Yes. That would be a complete sentence with a different focus:

Greșeala este interesantă pentru toți elevii.
= The mistake is interesting for all the students.

Original sentence:

Profesoara explică de ce greșeala este interesantă pentru toți elevii. = The teacher explains why the mistake is interesting for all the students.

So:

Without Profesoara explică de ce, you just state a fact.
With it, you’re talking about what the teacher is explaining (the reason).

What exactly does pentru mean in pentru toți elevii? Could I use another preposition?

pentru usually corresponds to English “for”.

In this sentence:

pentru toți elevii = for all (the) students

Other options (with a slightly different structure) exist, but they change the grammar:

tuturor elevilor (dative, without pentru)
- Greșeala este interesantă tuturor elevilor.
  = The mistake is interesting to all (the) students.

But if you use pentru, it must be followed by the accusative form:

pentru elevi, pentru toți elevii, pentru mine, etc.

So pentru is the natural choice here and works the same way as “for” in English.

Why is it toți elevii and not toate elevii?

Because elevii is grammatically masculine plural.

Singular: elev – (school) student, pupil
Plural: elevi
Definite plural: elevii – the students/pupils

The quantifier all has to agree in gender and number:

Masculine plural: toți
Feminine plural: toate

Examples:

toți elevii – all (the) students (mixed group or all male)
toate fetele – all (the) girls

So toți elevii is correct because elevii is masculine plural.

What is the difference between elev and student in Romanian?

Romanian distinguishes between types of students more clearly than English:

elev – a pupil or student in primary, middle, or high school
- elev de liceu – high school student
student – a student in university or other higher education

In your sentence, elevii refers to school pupils/students, not university students.
To say “all the university students”, you’d say toți studenții.

Why is there no word for “she” before explică? Shouldn’t it be Ea explică?

Romanian is a pro‑drop language: subject pronouns are usually omitted when the verb form already shows the person.

(Ea) explică. – (She) explains / is explaining.

Because the verb ending -ă in explică already tells us it’s 3rd person singular, you normally don’t add ea unless you want to emphasize it:

Ea explică, nu el. – She is explaining, not him.

In your sentence, the subject is expressed by Profesoara, so a separate ea would be redundant:

Profesoara explică… (normal)
Profesoara ea explică… (incorrect / sounds very strange)

Are the diacritics in greșeala, interesantă, and toți important? What happens if I write without them?

The diacritics are important and should be used:

ș vs s → greșeala vs greseala
ă vs a → interesantă vs interesanta
ț vs t → toți vs toti

Usually, people will still understand you if you omit them (Romanians are used to seeing text without diacritics), but:

It is not standard in formal writing.
Sometimes different words become ambiguous without diacritics.
For a learner, it’s better to always include them to learn correct spelling and pronunciation.

So the correct, fully written sentence is:

Profesoara explică de ce greșeala este interesantă pentru toți elevii.