El anillo es de oro.

In Spanish, articles are used more often than in English. El anillo means the ring.

If you said just anillo, it would sound less natural in a normal sentence unless it appeared in a special context, like a label, a dictionary entry, or a short note.

So:

• el anillo = the ring
• un anillo = a ring

Because anillo is a masculine noun, so it takes the masculine singular article el.

There is no deep logical reason why many nouns are masculine or feminine; it is something you usually learn together with the noun. In this case:

• el anillo = masculine
• plural: los anillos

The ending -o often suggests a masculine noun, and anillo follows that common pattern.

Es is the he/she/it form of the verb ser in the present tense.

The subject is el anillo, which is third-person singular, so Spanish uses es:

• yo soy
• tú eres
• él / ella / usted es

So El anillo es... means The ring is...

Spanish uses ser for essential characteristics, identity, origin, material, and what something is made of.

Here, de oro tells us the material of the ring, so ser is the correct verb:

• El anillo es de oro. = The ring is made of gold.

You would not normally use estar for this meaning.

A useful rule:

• ser = what something is, what it is made of
• estar = where something is, or a temporary state

Here de means something like of or made of.

So:

• de oro = of gold / made of gold

In Spanish, de is very commonly used to show material:

• una mesa de madera = a wooden table / a table made of wood
• una camisa de algodón = a cotton shirt

Because when Spanish talks about the material something is made of, it usually uses just de + material noun, with no article.

So you say:

• de oro
• de plata
• de madera

Not normally:

• del oro in this sentence

Del means de + el, but that is not the usual structure when naming the material in a general way.

Yes. In natural English, the idea is usually The ring is made of gold, but The ring is gold can also express the same basic meaning depending on context.

In Spanish, es de oro clearly tells you the ring’s material.

This is the normal Spanish word order:

• subject: El anillo
• verb: es
• complement: de oro

So it follows the same basic pattern as English:

• The ring / is / made of gold

Spanish can sometimes change word order for emphasis, but this standard order is the most natural here.

A common pronunciation in Spain is approximately:

• ah-NEE-yo

More specifically:

• a like the a in father
• ni sounds like nee
• ll in most modern Spanish accents sounds like an English y
• stress falls on ni: a-NI-llo

So the whole sentence is roughly:

• el ah-NEE-yo es deh OH-ro

The plural is:

Los anillos son de oro.

Changes:

• el → los
• anillo → anillos
• es → son

So:

• El anillo es de oro. = The ring is made of gold.
• Los anillos son de oro. = The rings are made of gold.

Yes, grammatically you can, but it means A ring is made of gold or One ring is made of gold, depending on context.

That changes the meaning:

• El anillo es de oro. = a specific ring, the ring
• Un anillo es de oro. = an unspecified ring, a ring

So if you are talking about one particular ring that both speakers know, el anillo is the right choice.

Oro is a noun here. It means gold.

In de oro, Spanish uses the noun after de to express material:

• de oro = of gold
• de plata = of silver

English often uses a noun like an adjective in phrases such as gold ring, but Spanish usually prefers structures like:

• anillo de oro = gold ring

So in this sentence, oro is still a noun, not an adjective.