El siglo empezó con un cambio.

El is the definite article, meaning the. Spanish uses it here because it refers to a specific century, not just any century in general.

So:

• el siglo = the century
• un siglo = a century

In this sentence, the speaker has a particular century in mind.

Nouns in Spanish have grammatical gender, and siglo is simply a masculine noun, so it takes masculine articles and adjectives:

• el siglo
• un siglo

There is no special rule here that would let you predict it easily from the form, so it is best learned together with the article: el siglo.

Empezó is the preterite tense, third person singular, from the verb empezar.

It means:

• he/she/it started
• you (formal) started

In this sentence, the subject is el siglo, so empezó means the century started / began.

Because the sentence is describing the beginning of the century as a completed event in the past, Spanish uses the preterite:

• empieza = present: starts / is starting
• empezaba = imperfect: was starting / used to start
• empezó = preterite: started / began

Here, the idea is a clear past event: the century began with something.

The accent mark shows where the stress goes: em-pe-ZÓ.

It is also important because it distinguishes this form from other forms:

• empezo would be incorrect
• empezó = he/she/it started

In Spanish spelling, the accent often helps show the correct pronunciation and the exact verb form.

The infinitive is empezar, meaning to start or to begin.

Some common forms are:

• empezar = to start
• empiezo = I start
• empieza = he/she starts
• empezó = he/she started
• empezaron = they started

The preposition con means with, so con un cambio means with a change.

This matches English quite closely:

• Empezó con un cambio = It started with a change

The preposition con is the normal one to use with empezar when you mean that something begins by having something as its first feature or element.

Because cambio is a masculine noun.

So you say:

• un cambio = a change
• el cambio = the change

Not:

• una cambio ❌

Again, it is best to learn the noun with its article: el cambio.

Yes. Comenzó and empezó are both natural here and both mean began / started.

• El siglo empezó con un cambio
• El siglo comenzó con un cambio

Both are correct. Empezar is often felt as slightly more everyday, while comenzar can sound a little more formal in some contexts, but the difference is small.

Yes. Empezar can be used with people, events, periods of time, activities, films, classes, and many other things.

Examples:

• La película empezó tarde. = The film started late.
• La clase empezó a las nueve. = The class started at nine.
• El año empezó bien. = The year started well.

So El siglo empezó... is completely natural.

The normal word order here is:

• El siglo
  • empezó
    • con un cambio

That is the most neutral order.

But Spanish can sometimes change word order for style or emphasis, for example:

• Con un cambio empezó el siglo.

This is possible, but it is more marked or literary. For a learner, the original order is the safest and most natural.

In Spain, siglo is pronounced roughly like SEE-glo, but with a Spanish g sound that is softer than the English g in go.

A helpful breakdown:

• siglo → SEE-glo
• stress on the first syllable: SI-glo

Also, in Spain, the c in cambio is pronounced like an English k, because it comes before a.

Usually, yes: siglo means century.

For example:

• el siglo XX = the 20th century
• el siglo XXI = the 21st century

In some contexts it can also be used more loosely in historical or literary language, but the main meaning is a 100-year century.

Spanish often leaves out subject pronouns because the verb ending already shows the person and number.

Here, the subject is explicitly stated as El siglo, so there is no need for any pronoun.

Spanish normally prefers:

• El siglo empezó con un cambio.

Not:

• Él siglo empezó... ❌

Also, él with an accent means he, while el without an accent means the.

Yes. Cambio is a broad word and can mean many kinds of change depending on context:

• a political change
• a social change
• a personal change
• a change in direction

So un cambio here is general and does not specify what kind of change unless more context is given.