Cuando mi profesor leyó el resumen, sonrió y me dijo que el título era claro y natural.

Cuando means when here and introduces a time clause: Cuando mi profesor leyó el resumen = When my teacher read the summary.

In Spanish, when this kind of time clause comes first, it is normally followed by a comma, just like in English:

• Cuando llegó, me llamó.
• When he arrived, he called me.

If the main clause comes first, the comma is usually not needed:

• Mi profesor sonrió cuando leyó el resumen.

Leyó is the preterite of leer and presents the action as a completed event: the teacher read the summary, and that action is seen as finished.

• leyó = read as a completed action
• leía = was reading / used to read / read in an ongoing or background sense

In this sentence, the teacher reads the summary, then smiles, then speaks. That sequence of completed actions makes the preterite the natural choice:

• leyó
• sonrió
• dijo

If you used leía, it would sound more like background information:

• Cuando mi profesor leía el resumen, sonreía...
• When my teacher was reading the summary, he was smiling...

That gives a different feel.

For the same reason as leyó: sonrió describes a single completed action in the sequence of events.

The sentence tells a story:

1. He read the summary.
2. He smiled.
3. He told me something.

Spanish commonly uses the preterite for this kind of narrative sequence.

• sonrió = he/she smiled

Its infinitive is sonreír.

This is one of the most useful questions in the whole sentence.

Dijo is preterite because it is a completed speaking event: he said something.

But era is imperfect because it describes how the title was in his view: clear and natural. Spanish often uses the imperfect for descriptions, characteristics, or states.

So:

• dijo = the act of saying happened and finished
• era claro y natural = this describes the title’s quality

Using fue would make it sound more like a completed event or result, not a descriptive quality. After dijo que, Spanish very often uses the imperfect when reporting a description or opinion that was expressed:

• Me dijo que la idea era buena.
• She told me the idea was good.

That sounds more natural than fue buena in this context.

Because decir que means to say that.

• me dijo que el título era claro y natural
• he told me that the title was clear and natural

In Spanish, que is very commonly used to introduce reported speech or reported statements.

Compare:

• Me dijo que vendría. = He told me that he would come.
• Dijo que estaba cansado. = He said that he was tired.

English often drops that, but Spanish usually keeps que.

Yes. The original sentence uses reported speech:

• ...me dijo que el título era claro y natural.

A direct-speech version could be:

• ...sonrió y me dijo: El título es claro y natural.

Notice the differences:

• Reported speech: era
• Direct speech: often es, because you are giving the exact words more directly

Both are possible, but the original sentence sounds very natural in normal narration.

Me means to me.

• dijo = said / told
• me dijo = told me / said to me

Spanish often uses an indirect object pronoun where English uses to + person:

• Me dijo... = He told me
• Te dijo... = He told you
• Nos dijo... = He told us

So me shows who received the information.

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

In this sentence:

• leyó
• sonrió
• dijo

all clearly mean he/she in context, and mi profesor has already been mentioned, so there is no need to say él.

Spanish usually includes subject pronouns only for emphasis, contrast, or clarity.

For example:

• Cuando mi profesor leyó el resumen, él sonrió...

This is grammatically possible, but normally unnecessary unless you want to stress he.

In this sentence, the definite articles are natural because both nouns refer to specific things in the context:

• el resumen = the specific summary
• el título = the specific title

Spanish uses articles very often, sometimes more often than English. Here they are definitely expected.

You would not normally say:

• leyó resumen
• título era claro

Those sound incomplete or ungrammatical here.

It can mean either, depending on context.

In Spanish, profesor is a general word for a teacher, especially in secondary school or higher education. English separates teacher and professor more strongly than Spanish often does.

So mi profesor could mean:

• my teacher
• my professor

If the meaning has already been shown to the learner, then the context has already decided which one is intended.

Because cuando has no accent when it is used as a conjunction meaning when.

• Cuando mi profesor leyó el resumen... = When my teacher read the summary...

It gets an accent — cuándo — in questions or exclamations:

• ¿Cuándo llegó? = When did he arrive?
• No sé cuándo llegó. = I don’t know when he arrived.

So:

• cuando = when
• cuándo = when? / at what time

They have accent marks to show the correct stress.

• leyó
• sonrió

Without the accent, the pronunciation and stress would be unclear or incorrect.

These are third-person singular preterite forms:

• leer → leyó
• sonreír → sonrió

The written accent helps show that the stress falls on the last syllable:

• le-YÓ
• son-ri-Ó

This is especially important in past-tense forms.

Because Spanish changes y to e only before words that begin with an i sound.

Examples:

• padre e hijo
• español e inglés

But natural starts with an n sound, so the normal conjunction is y:

• claro y natural

No change is needed.

Not here. In this context, natural means something like:

• natural-sounding
• not forced
• idiomatic
• smooth

So el título era claro y natural means the title sounded clear and well-phrased, not awkward.

This is a very common use of natural in language learning and writing feedback.

Yes. It is very straightforwardly ordered:

1. mi profesor leyó el resumen
2. sonrió
3. me dijo que...

Spanish often uses the preterite this way to narrate a sequence of finished events. That makes the sentence easy to follow and very natural for storytelling or reporting what happened.

Yes, both are possible depending on how natural you want the English to sound.

• sonrió y me dijo literally = smiled and said to me
• more natural English = smiled and told me

Since me dijo que... is followed by a clause, English often prefers told me that... or simply said that... to me, though told me sounds smoother in most cases.

Because Spanish, like English, can coordinate multiple actions after the same subject without repeating everything.

The subject mi profesor applies to all three verbs:

• leyó
• sonrió
• dijo

So the full underlying structure is:

• Cuando mi profesor leyó el resumen, mi profesor sonrió y mi profesor me dijo...

But repeating mi profesor each time would sound heavy and unnatural. Spanish normally omits repeated subjects when the reference is clear.