Le professeur dit que « a » est une voyelle et que « b » est une consonne.

Le professeur means the teacher/professor in the masculine form.

A few useful points:

• professeur has traditionally been used for both male and female teachers in some contexts.
• In modern French, you may also see la professeure for a female teacher.
• So this sentence uses a masculine or gender-neutral version: Le professeur.

If the teacher were clearly female, many learners today may also encounter:

• La professeure dit que...

Here, que means that.

So:

• Le professeur dit que... = The teacher says that...

French uses que very often to introduce a clause after verbs like:

• dire = to say
• penser = to think
• croire = to believe

In English, that is sometimes optional:

• The teacher says that...
• The teacher says...

In French, que is normally required here.

In this sentence, French repeats que before the second clause:

• Le professeur dit que a est une voyelle et que b est une consonne.

Literally:

• The teacher says that a is a vowel and that b is a consonant.

In English, you can sometimes omit the second that:

• ...that a is a vowel and b is a consonant.

In French, repeating que is very natural and often preferred, especially when it makes the sentence clearer. You may sometimes see omission in other contexts, but here the repeated que is standard and elegant.

Est is the verb être (to be) in the il/elle/on form.

Here the subject is the letter itself:

• a est une voyelle
• b est une consonne

French often uses X est Y when defining or classifying something directly.

Why not c'est?

• C'est is also possible in many situations, especially in spoken French, but a est une voyelle is a straightforward grammatical definition.
• In a formal explanation about letters, est works very naturally.

So this sentence is treating a and b as grammatical subjects and defining what they are.

French usually needs an article before singular countable nouns.

So:

• une voyelle = a vowel
• une consonne = a consonant

You generally cannot say just:

• a est voyelle
• b est consonne

That would sound incomplete in standard French.

Also:

• voyelle is feminine, so it takes une
• consonne is feminine too, so it also takes une

You can tell from the article:

• une voyelle
• une consonne

The article une marks a feminine singular noun.

There is not always a reliable way to guess noun gender from the ending alone, so it is best to learn nouns together with their article:

• une voyelle
• une consonne
• un mot
• une lettre

That makes it much easier to build correct sentences later.

The quotation marks show that the sentence is talking about the letters themselves, not using them as part of a word.

In English, we also often do this:

• “a” is a vowel
• “b” is a consonant

In French, you may see different styles of quotation marks:

• « a »
• "a"

The French-style marks « » are called guillemets.

A simple pronunciation guide is:

Le professeur dit que a est une voyelle et que b est une consonne.
Approx.: luh պրoh-feh-SUR dee kuh ah eh tune vwah-YELL ay kuh bay eh tune kohn-SOHN

A few details:

• Le ≈ luh
• professeur ≈ pro-feh-sur
• dit = dee
• que = kuh
• a = the name of the letter, pronounced ah
• est before a consonant is usually pronounced eh
• une is hard for English speakers; it is not exactly oon
• voyelle ≈ vwah-yell
• et = ay
• b = the name of the letter, pronounced bay
• consonne ≈ kon-son

Yes, there can be.

The most noticeable one is in:

• est une

Often pronounced roughly as:

• eh-tune

That extra t sound links est and une. This is called liaison.

So:

• a est une voyelle
• b est une consonne

may sound like:

• a eh-tune voyelle
• b eh-tune consonne

This is normal and useful to recognize when listening.

Because dire means to say, while parler means to speak.

• Le professeur dit que... = The teacher says that...
• Le professeur parle... = The teacher speaks/is speaking...

Since the sentence reports exactly what the teacher states, dit is the right verb.

Dit is the present tense of dire:

• je dis
• tu dis
• il/elle/on dit
• nous disons
• vous dites
• ils/elles disent

So Le professeur dit... means:

• The teacher says... or sometimes, depending on context,
• The teacher is saying...

Yes. Depending on context, professeur can mean:

• teacher
• professor

In everyday French, especially in schools, it often means teacher.

So without context, Le professeur could be:

• the teacher
• the professor

You understand the exact meaning from the situation.

Because this sentence follows a very common French pattern that matches English closely:

• Subject + verb + que + clause + et que + clause

So:

• Le professeur = subject
• dit = verb
• que... = first reported clause
• et que... = second reported clause

That is why this sentence feels relatively easy for English speakers compared with some other French structures.