Tengo veintitrés años.

In Spanish, age is expressed with tener (to have), not ser or estar.

So Spanish says:

• Tengo veintitrés años = literally I have 23 years

This is just the normal Spanish structure. English uses to be for age, but Spanish uses to have.

That is why Soy veintitrés años and Estoy veintitrés años are wrong for saying your age.

Usually, no. Spanish often leaves out subject pronouns when they are not needed, because the verb ending already shows who the subject is.

• Tengo = I have
• Yo tengo = I have too, but with extra emphasis

So:

• Tengo veintitrés años is the most natural neutral sentence.
• Yo tengo veintitrés años may be used for emphasis, contrast, or clarity.

Example:

• Ella tiene veinte años y yo tengo veintitrés.

Because the age is 23, which is more than one, so Spanish uses the plural noun años.

Compare:

• Tengo un año = I am one year old
• Tengo veintitrés años = I am twenty-three years old

So:

• 1 → año
• 2 or more → años

Sometimes, yes, but it depends on context.

• Tengo veintitrés años is the full, standard form.
• Tengo veintitrés is possible if everyone already knows you are talking about age.

For a learner, it is safest to use the full version:

• Tengo veintitrés años

That sounds complete and natural in all situations.

Spanish does not need a separate word like old when giving age.

English says:

• I am 23 years old

Spanish simply says:

• Tengo 23 años

The idea of age is already built into the expression with tener + number + años, so no extra word is needed.

A simple pronunciation guide is:

• Tengo ≈ TEN-go
• veintitrés ≈ bein-tee-TRES
• años ≈ AN-yos

A few useful notes:

• The stress in veintitrés falls on the last syllable: -trés
• The ñ in años sounds like the ny in canyon
• In much of Spain, the z sound in words like veintitrés is not relevant here, because this word has s, not z
• The g in tengo is a hard g, like in go

The accent mark shows where the stress goes: veintitrés.

Without getting too technical, it helps mark the correct pronunciation. You should stress the last syllable:

• veintiTRÉS

This written accent is part of the correct spelling.

A useful pattern:

• veintidós
• veintitrés
• veintiséis

These all have written accents.

You keep the same structure and change the number:

• Tengo dieciocho años = I am 18
• Tengo treinta años = I am 30
• Tengo cuarenta y dos años = I am 42

The pattern is:

Tengo + number + año/años

Be careful with 1:

• Tengo un año not Tengo uno años

Also:

• Tengo veintiún años = I am 21

Before a masculine noun like años, veintiuno changes to veintiún.

Yes. In informal writing, forms, messages, or notes, Tengo 23 años is completely normal.

In full written Spanish, especially in learning materials or more formal writing, the number is often written out:

• Tengo veintitrés años

So both are correct:

• Tengo 23 años
• Tengo veintitrés años

Yes. Tengo veintitrés años is standard Spanish everywhere.

The grammar is the same across the Spanish-speaking world for this expression:

• tener + number + años

The main differences you may notice are pronunciation and accent, not grammar.

The normal order is:

Tengo veintitrés años

Spanish can sometimes change word order for emphasis, but that is less neutral and less common for learners.

For example:

• Veintitrés años tengo sounds marked or poetic, not like the usual everyday way to answer the question.

So the best default word order is:

• Tengo veintitrés años

Most commonly, it answers:

• ¿Cuántos años tienes? = How old are you?

Then you reply:

• Tengo veintitrés años.

In conversation, you may also hear:

• ¿Qué edad tienes? = What age are you?/How old are you?

But ¿Cuántos años tienes? is extremely common and very useful to learn with this sentence.

Año is masculine:

• el año
• los años

That matters mainly with numbers like 21, where the form changes before a masculine noun:

• veintiún años not veintiuno años

It also matters with adjectives and articles in other contexts, but in Tengo veintitrés años, you do not need to change anything because veintitrés stays the same.