La profesora soltó un suspiro y luego explicó la diferencia otra vez.

Spanish often leaves out subject pronouns when they are not needed, because the verb ending already gives information about the subject.

• soltó = she/he let out
• explicó = she/he explained

Using la profesora makes the subject explicit and identifies who did the actions. After that, Spanish does not need ella.

La profesora ella soltó... would sound unnatural in normal Spanish unless you were adding strong emphasis or contrast.

Profesora is the feminine form of profesor. Since the sentence is about a female teacher, Spanish uses:

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

This also explains the article la, which agrees with the feminine noun.

Both verbs are in the preterite, which is used here for completed actions in the past.

• soltó comes from soltar
• explicó comes from explicar

They are both third person singular forms:

• él/ella/usted soltó
• él/ella/usted explicó

The sentence tells a sequence of finished events:

1. the teacher sighed
2. then she explained the difference again

That is exactly the kind of situation where the preterite is very common.

Literally, soltar means something like to let go, to release, or to let out. So soltó un suspiro is literally she let out a sigh.

Yes, this is a natural and common expression in Spanish. It works much like English let out a sigh.

Other possible Spanish ways to express a similar idea are:

• suspiró = she sighed
• soltó un suspiro = she let out a sigh

The version in your sentence is slightly more vivid or descriptive.

Because Spanish normally needs an article with countable singular nouns in this kind of sentence.

• soltó un suspiro = she let out a sigh

Leaving out un here would sound incomplete or unnatural.

In English, article use can be a bit more flexible in some expressions, but in Spanish un suspiro is the normal form.

Spanish uses the definite article more often than English. Here, la diferencia refers to the difference that both speaker and listener already know about.

So:

• explicó la diferencia = she explained the difference

Saying just explicó diferencia would be ungrammatical here.

Luego means then, afterward, or later. It links the two actions and shows the order:

1. soltó un suspiro
2. luego explicó la diferencia otra vez

So luego helps signal what happened next.

Other words with a similar function are:

• después
• entonces

In this sentence, luego sounds completely natural.

Otra vez means again. In this sentence it modifies explicó:

• explicó la diferencia otra vez = she explained the difference again

Yes, the position can vary somewhat. For example:

• La profesora soltó un suspiro y luego otra vez explicó la diferencia
  This is possible, but less natural here.
• La profesora soltó un suspiro y luego explicó otra vez la diferencia
  Also possible.

The version with otra vez at the end is very natural and clear.

Yes. Otra vez and de nuevo often both mean again.

So you could say:

• ...explicó la diferencia otra vez
• ...explicó la diferencia de nuevo

Both are correct. In many contexts, the difference is very small or nonexistent. Otra vez is often a bit more everyday and conversational.

The accent marks show stress and also help distinguish these forms from others.

• soltó
• explicó

These are preterite third person singular forms, and the stress falls on the last syllable.

The accent is part of the standard spelling of these verb forms. Without it, the word would be spelled incorrectly.

Not naturally in this exact context. The sentence describes specific completed actions, so the preterite fits best:

• soltó
• explicó

If you used the imperfect:

• soltaba
• explicaba

it would suggest background, repetition, or an ongoing past situation rather than a single completed sequence.

So the preterite is the normal choice here.

Yes, Spanish word order is more flexible than English. You could say:

• Soltó un suspiro la profesora y luego explicó la diferencia otra vez.

But this is less neutral. The original sentence:

• La profesora soltó un suspiro y luego explicó la diferencia otra vez.

is the most straightforward and natural version in ordinary narration.

Putting the subject later can add a different rhythm or emphasis, but it is not necessary here.

It is not a single fixed unit in the sense of being inseparable, but y luego is a very common combination meaning and then.

• y = and
• luego = then / afterward

Together they smoothly connect two actions in sequence. It is one of the most natural ways to say and then in Spanish.

Sometimes yes, but not both in the same way.

For la diferencia, a pronoun is very possible:

• La profesora soltó un suspiro y luego la explicó otra vez.
• Here la = the difference

That is grammatical, though the original sentence may sound clearer.

For un suspiro, replacing it with a pronoun is less natural in this structure, because soltar un suspiro is a set expression and the full noun phrase sounds better.

So the original sentence is very natural as written.