La revocación cambia la disposición testamentaria.

Because revocación is being used as a specific noun phrase: the revocation.

In Spanish, the definite article el/la/los/las is often used more than in English, especially in formal, legal, or abstract language. So Spanish naturally says La revocación... where English might sometimes also say Revocation..., depending on style.

Also, revocación is a feminine noun, so it takes la.

Because nouns ending in -ción are almost always feminine in Spanish.

So:

• la revocación
• la disposición
• la decisión
• la obligación

That is a very useful pattern to remember.

The accent mark shows where the stress goes: re-vo-ca-CIÓN.

Without the written accent, Spanish stress rules would make you expect a different pronunciation. The accent tells you clearly that the last syllable is stressed.

In Spain, the final ción is pronounced roughly like:

• thyon in much of Spain
• syon in Latin America and some parts of Spain

So in standard Peninsular Spanish, revocación sounds approximately like reh-boh-kah-THYON.

Because the subject is la revocación, which is:

• third person
• singular

So the verb cambiar must be conjugated as cambia in the present indicative.

Here is the pattern:

• yo cambio
• tú cambias
• él/ella cambia
• nosotros cambiamos
• vosotros cambiáis
• ellos/ellas cambian

Since la revocación = it, the sentence uses cambia.

It can mean either, depending on context.

Spanish simple present often covers both:

• changes
• is changing

So La revocación cambia la disposición testamentaria could be understood as:

• The revocation changes the testamentary provision or
• The revocation is changing the testamentary provision

In a legal sentence like this, the more natural English translation is usually changes.

Because it is the direct object and it is being presented as a specific thing: the testamentary provision.

Spanish often uses the definite article where English does too, and in formal writing it helps mark the noun clearly:

• La revocación cambia la disposición testamentaria.

It sounds complete and natural. Without la, the sentence would generally sound wrong here.

It is a legal expression. It means something like:

• testamentary provision
• provision in a will
• clause in a will

A disposición in legal language is not just a general disposition in the English personality sense. Here it means a formal provision, arrangement, or clause.

And testamentaria means relating to a will/testament.

So together, disposición testamentaria is a technical legal phrase.

Because in Spanish, adjectives usually come after the noun, especially when they are:

• descriptive in a neutral way
• technical or classifying
• part of formal/legal language

So:

• disposición testamentaria literally follows the normal Spanish pattern:
• noun + adjective

This is much more natural than putting the adjective first.

Because adjectives must agree with the noun they describe.

The noun is disposición, which is feminine singular, so the adjective must also be feminine singular:

• disposición testamentaria
• not disposición testamentario

If the noun were masculine, then the adjective would change:

• documento testamentario

Because Spanish does not need a subject pronoun when the subject is already stated.

Here, the subject is explicitly named:

• La revocación

So adding ella would be unnecessary and unnatural:

• La revocación cambia... is correct
• Ella la revocación cambia... is wrong

Spanish normally uses either:

• the noun itself, or
• a pronoun if the noun is omitted and the context is clear

Yes, but La revocación cambia la disposición testamentaria is the most neutral and standard order:

• subject + verb + object

Other word orders are possible in Spanish for emphasis or style, especially in formal writing, but they are less neutral. For a learner, this sentence is a very good model of standard word order.

Because the personal a is normally used before a specific human being (and sometimes pets or personified beings), not before things or abstract legal concepts.

Compare:

• Veo a la abogada. = I see the lawyer.
• Veo la disposición testamentaria. = I see the testamentary provision.

In your sentence, la disposición testamentaria is not a person, so no a is used.

Not really. It is grammatical and correct, but it sounds formal and legal.

Words like:

• revocación
• disposición testamentaria

belong more to legal or administrative Spanish than everyday conversation.

A native speaker would understand it, but they would recognize it as legal language rather than casual speech.