La profesora disculpó mi retraso.

Because Spanish normally uses a definite article with a specific subject like this: la profesora = the teacher.

If you said just profesora, it would usually only work in special contexts, for example when directly addressing someone or in note-like style. In a normal full sentence, la profesora sounds natural.

• La profesora disculpó mi retraso. = The teacher excused my lateness.

Also, profesora is the feminine form of profesor.

Because the sentence is referring to a female teacher.

• el profesor = the male teacher
• la profesora = the female teacher

In Spanish, many nouns for people change form depending on gender, and the article changes too:

• el profesor
• la profesora

Disculpó is the preterite tense, third person singular, from disculpar.

So it means:

• he/she excused
• in this sentence: the teacher excused

The preterite is used for a completed action in the past. Here, the teacher did one finished action: she excused the lateness.

Full verb pattern:

• yo disculpé
• tú disculpaste
• él/ella/usted disculpó
• nosotros disculpamos
• vosotros disculpasteis
• ellos/ellas/ustedes disculparon

The accent mark shows both pronunciation and meaning.

• disculpo = I excuse / I am excusing (present)
• disculpó = he/she excused (preterite)

So the accent helps distinguish:

• present first person singular
• past third person singular

This is a very common pattern in Spanish:

• hablo / habló
• llamo / llamó
• disculpo / disculpó

No. In this sentence, disculpar means to excuse or to forgive.

That can confuse English speakers, because to excuse and to apologize are different in English.

Compare:

• La profesora disculpó mi retraso. = The teacher excused my lateness.
• Me disculpé. = I apologized.

So:

• disculpar algo / a alguien = to excuse something / someone
• disculparse = to apologize

Because mi is a possessive adjective meaning my.

• mi retraso = my delay / my lateness

But me is an object pronoun meaning me, and it would not fit here.

So:

• mi = my
• me = me

This sentence needs the possessive form because it is talking about your lateness, not doing something to you.

Here, retraso means delay or lateness.

In this sentence, mi retraso is best understood as my lateness or my being late.

The noun retraso is broader than just arriving late to class. In other contexts it can mean many kinds of delay:

• el retraso del tren = the train delay
• un retraso en el proyecto = a delay in the project

But in this sentence, with a teacher, it naturally means lateness.

Because disculpar can take a direct object directly.

So Spanish can say:

• disculpar algo = to excuse something
• disculpar a alguien = to excuse someone

That is why mi retraso appears directly after the verb:

• La profesora disculpó mi retraso.

A slightly different structure is also possible in Spanish, for example:

• La profesora me disculpó por el retraso.

That shifts the focus a bit toward me as the person being excused. But your original sentence is perfectly grammatical and straightforward.

Because mi retraso is a thing/idea, not a person.

The personal a is normally used before a specific human direct object:

• Veo a la profesora. = I see the teacher.

But here the direct object is mi retraso (my lateness), which is not a person:

• La profesora disculpó mi retraso.

So no a is needed.

This is the most neutral and common Spanish word order:

subject + verb + object

• La profesora = subject
• disculpó = verb
• mi retraso = direct object

Spanish does allow more flexibility than English, but this order is the clearest and most standard here.

Yes. Profesora can sometimes be translated as teacher or professor, depending on context.

• In a school context: usually teacher
• In a university context: often professor

So the best English translation depends on the situation, even though the Spanish stays the same.

The preterite is used because the sentence describes a completed event: the teacher excused the lateness.

• disculpó = she excused it, one finished action

If you used the imperfect, disculpaba, it would sound more like:

• she was excusing
• she used to excuse
• she would excuse

That would suggest an ongoing, repeated, or background action, which is not the usual meaning here.

Yes, excusar exists and can also mean to excuse, but disculpar is very common and natural.

There can be slight differences in tone or usage depending on region and context, but for a learner, the key point is:

• disculpar = to excuse / forgive
• excusar = to excuse

In Spain, disculpar is very common in everyday language, and this sentence sounds natural.

Not exactly. Your sentence means more literally:

• The teacher excused my lateness

If you want to focus on me as the person, Spanish often uses a different structure, such as:

• La profesora me disculpó por llegar tarde.
• La profesora me disculpó por el retraso.

So the original sentence focuses on the lateness itself, while those versions focus more on you. Both ideas are closely related, but they are not structured in exactly the same way.