Mi vecino es alemán.

Because ser is used for identity, origin, and nationality. In Mi vecino es alemán, alemán describes what your neighbor is by nationality, so Spanish uses es from ser.

A useful rule:

• ser = identity, nationality, profession, essential characteristics
• estar = location, condition, temporary states

So:

• Mi vecino es alemán = correct
• Mi vecino está alemán = not correct for nationality

In Spanish, when you say someone is a nationality, religion, or many professions after ser, you usually do not use an article.

So Spanish says:

• Mi vecino es alemán not
• Mi vecino es un alemán in the normal neutral sense

Using un here can sound more specific or emphatic, like He is a German man, rather than simply stating nationality.

In Spanish, nationalities and languages are normally written in lowercase, unlike in English.

So:

• alemán
• mexicano
• español
• inglés

They are only capitalized if they begin a sentence.

Yes. Vecino is the masculine singular form, so it normally refers to a male neighbor.

If the neighbor is female, you would usually say:

• Mi vecina es alemana

Notice that both words change:

• vecino → vecina
• alemán → alemana

Because mi is the possessive form used before a noun.

• mi vecino = my neighbor

Mío is used differently, usually on its own or after a noun:

• El vecino es mío = The neighbor is mine (unnatural in many real situations, but grammatically possible)
• un amigo mío = a friend of mine

So before vecino, you need mi.

Here, alemán is functioning as an adjective of nationality after ser.

In Spanish, nationality words can often work as both:

• adjectives: un coche alemán = a German car
• nouns for people: un alemán = a German man

In Mi vecino es alemán, it is best understood as a nationality adjective describing mi vecino.

The accent mark shows where the stress goes: a-le-MÁN.

Without the written accent, Spanish spelling rules would suggest a different stress pattern. The accent tells you that the last syllable is stressed.

It also helps when the word changes in the plural:

• alemán → alemanes

Notice that the accent disappears in the plural form.

A simple Latin American-style pronunciation guide is:

mee beh-SEE-no ess ah-leh-MAHN

A few details:

• mi sounds like mee
• vecino usually sounds like beh-SEE-no in Latin America
• es sounds like ess
• alemán has the stress on the last syllable: -mán

Yes. That is also correct.

There is a small difference in style:

• Mi vecino es alemán = states nationality directly
• Mi vecino es de Alemania = literally My neighbor is from Germany, focusing on place of origin

Both are natural, and in many situations they mean almost the same thing.

Because Spanish often does not need an extra subject pronoun when the subject is already clear.

In this sentence, the subject is already stated:

• Mi vecino

So there is no need to add él.

You could say:

• Mi vecino es alemán

Not normally:

• Él mi vecino es alemán = incorrect

If you wanted to use él, you would usually replace the noun phrase, not stack both in that way:

• Él es alemán = He is German

The normal word order is:

• Mi vecino es alemán

That is the most neutral and natural order.

You might hear changes in special contexts for emphasis, but for a learner, it is best to stick with:

• possessive + noun + ser
  • nationality

So:

• Mi vecino es alemán = standard
• Alemán es mi vecino = possible only in very marked or poetic contexts, not normal everyday speech

If you are talking about more than one neighbor, the sentence changes like this:

• Mis vecinos son alemanes = My neighbors are German

Changes:

• mi → mis
• vecino → vecinos
• es → son
• alemán → alemanes

If they are all female:

• Mis vecinas son alemanas