Tuve que pedir perdón por llegar tarde a la reunión.

Tuve que means I had to.

It comes from tener que + infinitive, which is a very common way to express obligation:

• Tengo que estudiar = I have to study
• Tuve que pedir perdón = I had to ask for forgiveness / apologize

So the structure here is:

• tuve que = I had to
• pedir perdón = apologize / ask forgiveness

This is a very common question because both can translate as had to in English.

• Tuve que pedir perdón uses the preterite
• Tenía que pedir perdón uses the imperfect

The difference is about how the obligation is viewed:

• Tuve que... = the obligation came up as a completed event, and it usually suggests the action was actually carried out.
• Tenía que... = I had to / was supposed to..., but it does not clearly say whether I actually did it.

So:

• Tuve que pedir perdón = I had to apologize, and the sentence strongly suggests that I did.
• Tenía que pedir perdón = I needed to apologize / was supposed to apologize, but maybe I hadn’t done it yet.

Because Spanish often leaves out subject pronouns when the verb already makes the subject clear.

• Tuve already tells us it is I because it is the 1st person singular preterite form of tener.

So:

• Tuve que pedir perdón...
• Yo tuve que pedir perdón...

Both are correct, but the version without yo is more natural unless you want emphasis or contrast:

• Yo tuve que pedir perdón, pero él no.
  = I had to apologize, but he didn’t.

Pedir perdón literally means to ask for forgiveness, but in many contexts it simply means to apologize.

It is a very common expression in Spanish.

Examples:

• Te pido perdón. = I ask your forgiveness / I’m sorry.
• Tuve que pedir perdón. = I had to apologize.

So even though the literal wording is different from English, the practical meaning is often just to apologize.

Because the two verbs do different jobs:

• pedir perdón = to ask for forgiveness / to apologize
• perdonar = to forgive

So in this sentence, the speaker is the person who did something wrong and had to apologize. That is why Spanish uses pedir perdón, not perdonar.

Compare:

• Tuve que pedir perdón. = I had to apologize.
• Tuve que perdonarlo. = I had to forgive him.

Yes, pedir perdón is a standard expression, and normally you do not use an article there.

So Spanish says:

• pedir perdón
• pedir disculpas

not usually:

• pedir el perdón in this normal everyday sense

Using el perdón is possible in other contexts, but it would sound more formal, literary, or specific. For everyday apology, pedir perdón is the natural choice.

Yes, absolutely.

Both are common:

• pedir perdón
• pedir disculpas

They are often interchangeable, but there can be a slight nuance:

• pedir disculpas can sound a bit more neutral or formal
• pedir perdón can sound a bit more personal or emotional

So:

• Tuve que pedir perdón...
• Tuve que pedir disculpas...

Both are good Spanish.

Because por introduces the reason or cause here.

• por llegar tarde = because of arriving late / for arriving late

So the sentence means that the reason for the apology was arriving late.

This use of por + infinitive is very common in Spanish:

• Gracias por venir. = Thanks for coming.
• Lo castigaron por mentir. = He was punished for lying.
• Tuve que pedir perdón por llegar tarde. = I had to apologize for arriving late.

Because after a preposition like por, Spanish normally uses the infinitive, not a conjugated verb.

So:

• por llegar tarde = correct
• por llegué tarde = incorrect

This is similar to English using for arriving late, not for I arrived late.

After prepositions, Spanish commonly uses the infinitive:

• antes de salir = before leaving
• después de comer = after eating
• por llegar tarde = for arriving late

Yes, it could.

• por llegar tarde
• por haber llegado tarde

Both are possible, but they are not exactly the same in feel.

• por llegar tarde is the most natural and straightforward everyday phrasing
• por haber llegado tarde is more explicit about the action being completed before the apology, and can sound a bit more formal or precise

In normal conversation, por llegar tarde is usually enough.

Llegar tarde is a very common expression meaning to arrive late.

Here, tarde is an adverb, meaning late.

So:

• llegar tarde = to arrive late
• salir tarde = to leave late
• acostarse tarde = to go to bed late

Do not confuse this tarde with the noun tarde meaning afternoon. In this sentence, it clearly means late.

Because llegar normally goes with a when you say where someone arrives.

• llegar a la reunión = to arrive at the meeting
• llegar a casa = to arrive home
• llegar al aeropuerto = to arrive at the airport

So a la reunión belongs with llegar, not with pedir perdón.

The structure is:

• pedir perdón
• por llegar tarde a la reunión

In other words: apologize for arriving late to the meeting.

No, it does not. Spanish often leaves that out if it is obvious from context or not important.

If you want to include the person or people apologized to, you can add it:

• Tuve que pedir perdón a mis compañeros por llegar tarde a la reunión.
• Tuve que pedirles perdón a mis compañeros por llegar tarde a la reunión.

Both are possible. The second one includes the indirect object pronoun les.

Yes. Spanish allows some flexibility.

For example:

• Tuve que pedir perdón por llegar tarde a la reunión.
• Por llegar tarde a la reunión, tuve que pedir perdón.

Both are correct. The original order is very natural because it gives the main action first and the reason after it.

Putting por llegar tarde a la reunión first gives more emphasis to the reason.

Sometimes, yes, but tener que is the more direct and common way to say have to.

• Tuve que pedir perdón = I had to apologize
• Debí pedir perdón can mean I should have apologized or sometimes I must have apologized, depending on context, so it can be more ambiguous

Because of that, tener que is usually the safest and clearest choice when you mean real obligation.

So in this sentence, tuve que is the best straightforward option.