La canción es alegre.

La is the feminine singular definite article, meaning the.

You use la because canción is a feminine singular noun:

• la canción = the song

In Spanish, nouns have grammatical gender, so the article has to match the noun.

You usually learn the gender together with the noun: la canción, not just canción.

While many nouns ending in -o are masculine and many ending in -a are feminine, canción is one of the many feminine nouns ending in -ión. A lot of nouns with this ending are feminine:

• la canción
• la televisión
• la conversación

So it is best to memorise it as la canción.

Spanish has two main verbs meaning to be: ser and estar.

Here, es is used because alegre describes a general characteristic or quality of the song. It tells us what the song is like.

• es alegre = it is cheerful / it is a cheerful song

You would normally use ser for descriptions, identity, and more permanent or defining qualities.

Es is the third person singular form of ser in the present tense.

So:

• yo soy = I am
• tú eres = you are
• él/ella es = he/she is

Because la canción is singular, the verb must also be singular:

• La canción es alegre.

Some Spanish adjectives change form for gender, but others do not.

Alegre is an adjective with the same form for masculine and feminine singular:

• el niño alegre
• la niña alegre

It only changes for number:

• singular: alegre
• plural: alegres

So in this sentence, alegre stays the same even though canción is feminine.

Yes, it is possible, but it is less neutral.

The most basic and common structure is:

• La canción es alegre.

If you put the adjective before the noun, as in la alegre canción, it sounds more literary, poetic, or stylistically marked. It is not the usual way to say this simple idea in everyday speech.

So for a learner, La canción es alegre is the normal pattern to use.

The accent mark shows where the stress goes: can-CIÓN.

Without the accent, Spanish spelling rules would make you stress it differently. The written accent tells you the final syllable is stressed.

It is also important for correct spelling, so you should write:

• canción ✅
• cancion ❌

In Spain, a common pronunciation is roughly:

• la = lah
• canción = kan-thyon in much of Spain
• es = ess
• alegre = ah-LEH-greh

A few notes:

• The c before i in much of Spain sounds like the th in think, so ción sounds like thyon.
• The g in alegre is a hard g, like in get.
• The r in alegre is a light tapped r.

Normally, no.

In Spanish, singular countable nouns usually need an article or another determiner when you are speaking generally about a specific thing:

• La canción es alegre.

Leaving out the article here sounds unnatural. Spanish uses articles more often than English does in some cases.

It would become:

• Las canciones son alegres. = The songs are cheerful.

The changes are:

• la → las
• canción → canciones
• es → son
• alegre → alegres

Everything has to agree in number.

Yes. Alegre often means cheerful, lively, or joyful, not just happy in a personal emotional sense.

With canción, alegre usually suggests that the song sounds upbeat, bright, or cheerful.

So even if the English translation says happy, the Spanish adjective can carry the sense of cheerful or lively very naturally.