La sustitución no afecta a la antigüedad.

Spanish often uses the definite article more than English does, especially with abstract nouns or when talking about something in a general or institutional sense.

So:

• La sustitución = the substitution / replacement
• la antigüedad = the seniority / length of service

In English, you might sometimes drop the, but in Spanish it is very natural to keep it here.

This sentence sounds like it comes from a formal or legal/workplace context, where Spanish often uses articles with nouns in this way.

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

So:

• la sustitución
• la organización
• la situación
• la decisión

That is why the article is la, not el.

Because the verb afectar is commonly used with the preposition a before the thing or person affected:

• afectar a alguien
• afectar a algo

So in this sentence:

• afecta a la antigüedad = affects seniority

This a is just part of how the verb is normally constructed in Spanish. It is not the same as the English to in meaning; it is simply required by the verb here.

Because the subject is La sustitución, which is:

• third person
• singular

So the verb must also be third person singular:

• La sustitución afecta... = The substitution affects...

Compare:

• La sustitución afecta = singular subject
• Las sustituciones afectan = plural subject

And afectar is the infinitive, so it would not work here as the main finite verb.

In standard Spanish, no normally goes directly before the conjugated verb.

So:

• no afecta = does not affect

This is the normal word order for negation:

• No funciona.
• No entiendo.
• No afecta a la antigüedad.

Although antigüedad can sometimes mean antiquity or age/oldness, in work, legal, or administrative contexts it often means:

• seniority
• length of service
• time someone has been in a job or position

So in this sentence, it most likely refers to employment seniority, not to something ancient.

The two dots over ü are called a diaeresis. In Spanish, gue and gui normally make the u silent:

• guerra = geh-rra
• guiar = gee-ar

But with güe or güi, the u is pronounced:

• antigüedad
• pingüino
• vergüenza

So antigüedad is pronounced roughly an-tee-gwe-DAD.

Without the diaeresis, the pronunciation would be different.

A rough pronunciation is:

• soos-tee-too-THYON in most of Spain
• soos-tee-too-SYON in Latin American Spanish and some parts of Spain

A few key points:

• the stress falls on the last syllable because of the written accent: -ción
• ción is a very common ending in Spanish nouns

So the stressed part is:

• sus-ti-tu-CIÓN

The accent mark shows where the stress goes:

• sus-ti-tu-CIÓN

Without the accent, the stress rules would suggest a different pronunciation, so the written accent is needed.

Many Spanish nouns ending in -ción have this stress pattern:

• información
• situación
• condición
• sustitución

Sometimes yes, but not always with exactly the same tone or context.

• sustitución often sounds more formal, technical, administrative, or legal
• reemplazo can also mean replacement, but usage depends on region and context

In Spain, sustitución is very natural in official or formal wording, especially in employment or administrative language.

So in a sentence like this, sustitución sounds especially appropriate.

Yes. Afecta is the present tense of afectar.

But in formal Spanish, the present tense is often used to state a general rule, policy, or fact, not just something happening right now.

So La sustitución no afecta a la antigüedad means something like:

• Replacement does not affect seniority
• A replacement does not affect seniority
• The substitution does not affect seniority

It sounds like a rule or standing condition.

Yes. The thing being affected is la antigüedad.

Structure:

• La sustitución = subject
• no afecta = verb phrase
• a la antigüedad = the complement required by afectar, referring to what is affected

So the sentence means that the substitution has no effect on seniority.

Because al is the contraction of:

• a + el

But here the noun is feminine:

• la antigüedad

So:

• a + la = a la
  not al

Compare:

• afecta al trabajador = affects the worker
• afecta a la antigüedad = affects seniority

Yes. Antigüedad is a very context-dependent word. It can mean:

• seniority in work contexts
• length of service
• age or how old something is
• antiquity in historical contexts
• sometimes even an antique object in the plural: antigüedades

So learners should not assume it always means antiquity. In this sentence, seniority is the most likely meaning.