La puerta es morada.

Because puerta is a feminine noun in Spanish, so it takes the feminine singular article la.

• la puerta = the door
• el is used with masculine singular nouns, so el puerta is incorrect.

A useful habit is to learn nouns together with their article:

• la puerta
• la casa
• el libro
• el coche

The -a ending is a strong clue that a noun is feminine, and in this case it is. So puerta is feminine: la puerta.

However, it is not a perfect rule. Some Spanish nouns ending in -a are masculine, such as:

• el día
• el mapa

So the safest approach is to learn the noun with its article: la puerta.

Es is the third-person singular form of the verb ser, which means to be.

So:

• la puerta = the door
• es = is
• morada = purple

Together:

• La puerta es morada. = The door is purple.

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

Here, es is used because the sentence is describing a general characteristic of the door: its colour.

• La puerta es morada. = the door is purple

In beginner Spanish, ser is normally used for things like:

• identity
• description
• colour
• origin
• profession

Using estar with colours can sometimes suggest a temporary state or a special situation, but for a straightforward description of colour, ser is the normal choice.

Because Spanish adjectives usually agree with the noun they describe in gender and number.

Since puerta is:

• feminine
• singular

the adjective must also be:

• feminine
• singular

So:

• puerta morada = correct
• puerta morado = incorrect

Compare:

• El libro es morado. = The book is purple.
• La puerta es morada. = The door is purple.

The masculine singular form is morado.

Here are the main forms:

• morado = masculine singular
• morada = feminine singular
• morados = masculine plural
• moradas = feminine plural

Examples:

• El coche es morado.
• La puerta es morada.
• Los coches son morados.
• Las puertas son moradas.

In this sentence, yes: morada is an adjective meaning purple.

But in other contexts, morada can also be a noun meaning dwelling, residence, or home in a more literary or formal style.

For example:

• Esta es su morada. = This is his/her dwelling.

In La puerta es morada, though, it clearly means purple.

Because many Spanish adjectives change form to match the noun.

English says:

• the purple door
• the purple house

with purple staying the same.

Spanish often changes the adjective:

• la puerta morada
• el coche morado

This agreement is a very normal part of Spanish grammar.

Grammatically, Spanish adjectives can sometimes go before the noun, but with colours that is not the normal order.

The usual order is:

• la puerta morada = the purple door

And in your sentence, because the adjective comes after es, the structure is:

• La puerta es morada.

So for a basic colour description, stick with:

• la puerta morada
• la puerta es morada

A simple pronunciation guide for an English speaker is:

lah PWEHR-tah es moh-RAH-dah

A few helpful points:

• puerta begins with puer-, pronounced roughly pwehr-
• the r in morada is a light Spanish r, not a strong English r
• stress falls on:
  • PWER in puerta
  • RA in morada

Yes. In Spanish, it is normal to say La puerta es morada with the definite article la.

Spanish often uses articles where English might not focus on them as much. Since you are talking about the door, la is the natural choice.

If you wanted to say a door is purple, you would use:

• Una puerta es morada.

But for the door is purple, it is:

• La puerta es morada.