El remitente es chino.

Because remitente is a noun that can refer to either a male or a female sender. In Spanish, this kind of noun is often called a common-gender noun.

• el remitente = the sender, if male or unspecified
• la remitente = the sender, if female

So in El remitente es chino, the sentence is talking about a male sender, or a sender treated as grammatically masculine by context.

Usually, remitente itself stays the same. What changes is the article, and sometimes the adjective.

• el remitente es chino
• la remitente es china

So the noun remitente does not become something else like remitenta. The gender is shown by el/la and by adjectives like chino/china.

Because ser is used for things like identity, origin, nationality, and permanent characteristics.

Here, chino means Chinese, which is a nationality or origin, so Spanish uses ser:

• El remitente es chino.

Using estar here would sound wrong in standard Spanish, because nationality is not treated as a temporary condition.

In Spanish, words for nationalities and languages are normally not capitalized.

So Spanish writes:

• chino
• mexicano
• argentino
• español

This is different from English, where you write Chinese with a capital letter.

Yes. Adjectives in Spanish usually agree in gender and number with the noun they describe.

So you get:

• El remitente es chino.
• La remitente es china.
• Los remitentes son chinos.
• Las remitentes son chinas.

Even though remitente itself stays the same, the adjective chino/china/chinos/chinas changes.

Here it functions like an adjective of nationality after ser.

In El remitente es chino, chino describes the sender’s nationality.

English often does something similar with words like He is Chinese, but in Spanish this kind of word still follows normal agreement rules:

• Ella es china
• Ellos son chinos

Yes. That is also correct.

There is a small difference in feel:

• El remitente es chino = The sender is Chinese.
• El remitente es de China = The sender is from China.

In many situations they are very close in meaning, but es chino identifies nationality/ethnic identity more directly, while es de China focuses on place of origin.

Because this sentence is built as:

• subject: El remitente
• verb: es
• predicate adjective: chino

So chino is not directly sitting next to the noun; it is coming after ser to describe the subject.

If you put the adjective before or directly after the noun, you change the structure:

• El remitente chino... = The Chinese sender...
  This is now a noun phrase, not a complete sentence by itself unless more is added.

But:

• El remitente es chino. = The sender is Chinese.

In this full sentence, normally no.

Spanish usually needs the definite article with a noun like this when it is the subject:

• El remitente es chino.

If you just say Remitente es chino, it sounds incomplete or unnatural in standard Spanish.

However, in labels, forms, envelopes, or headings, you may see Remitente by itself, but that is not the same as a normal sentence.

A simple approximate pronunciation is:

el reh-mee-TEN-teh es CHEE-no

A few notes:

• r in remitente is a soft Spanish r
• te in remitente sounds like teh
• ch in chino sounds like English ch in chat
• Stress falls on:
  • remiTENte
  • CHIno

Not exactly in this form.

If the sender is known to be female, standard Spanish would usually say:

• La remitente es china.

The sentence El remitente es chino points to a masculine sender, or to a sender referred to with masculine grammar. So if you know the sender is a woman, you should normally change both the article and the adjective.