Cuando llego cansada, dejo el llavero en el recibidor y enciendo la lámpara del pasillo.

Because cansada agrees with the speaker. In this sentence, the speaker is understood to be female, so the adjective is feminine singular: cansada.

• llego cansada = I arrive tired (said by a woman)
• llego cansado = I arrive tired (said by a man)

Spanish adjectives often change to match the gender and number of the person or thing they describe.

Spanish often leaves out subject pronouns when they are not needed, because the verb ending already shows who the subject is.

• llego = I arrive
• dejo = I leave
• enciendo = I switch on / light

So yo is optional here. You could say Cuando yo llego cansada..., but it usually sounds more natural without yo unless you want emphasis or contrast.

The present tense here is being used for a habitual action or a routine.

• Cuando llego cansada, dejo... y enciendo... = When / Whenever I get home tired, I leave... and switch on...

This is very common in Spanish. The present tense can describe things you generally do, not just what you are doing right now.

It can suggest either, depending on context, but in a sentence like this it often has a general/habitual meaning close to whenever.

• Cuando llego cansada...
  = When I arrive tired... / Whenever I arrive tired...

If the sentence is talking about a repeated habit, English often prefers whenever, but when is also possible.

Because cansada describes the state in which the speaker arrives.

• llego cansada = I arrive tired

This is similar to English: I come home tired, I arrive exhausted, etc.

In Spanish, adjectives often follow verbs like llegar, salir, volver, and describe how someone is when that action happens.

Not exactly. Llavero usually means keyring, keychain, or key holder, not the keys themselves.

• las llaves = the keys
• el llavero = the keyring / keychain

In real life, people may sometimes use it loosely, but the basic meaning is the object the keys are attached to.

Recibidor means the entrance hall, foyer, or entryway of a home.

In Spain, recibidor is a very natural word for the area just inside the front door where you might leave keys, coats, or bags.

Depending on the house, English translations could be:

• entryway
• hall
• entrance hall
• foyer

Pasillo means hallway or corridor.

So:

• la lámpara del pasillo = the lamp in the hallway / the hallway lamp

In many homes, pasillo refers to the corridor connecting rooms.

Because de + el contracts to del.

So:

• de + el = del
• la lámpara del pasillo = the lamp of the hallway / the hallway lamp

This contraction is mandatory in standard Spanish.

The only common exception is when El is part of a proper name, such as de El Escorial.

Spanish uses definite articles more often than English does.

Here, the speaker is talking about specific, familiar things in the house:

• the keyring
• the entryway
• the lamp
• the hallway

Even where English might sometimes sound more natural with a possessive or no article at all, Spanish often prefers the definite article if the object is understood from context.

Yes. Encender is an irregular verb.

In the yo form:

• encender → enciendo

This is a stem-changing verb:

• e changes to ie in many forms

For example:

• yo enciendo
• tú enciendes
• él/ella enciende

But:

• nosotros encendemos
• vosotros encendéis

So the sentence uses the normal yo form of that irregular pattern.

In some Spanish-speaking regions, yes, but for Spain, encender is the safer and more standard choice for switch on / light.

In Spain, people commonly say:

• encender la luz
• encender la lámpara

In some parts of Latin America, prender la luz is very common. A learner focusing on Spain should prefer encender.

Because lámpara is more specific.

• la lámpara = the lamp
• la luz = the light

If you say enciendo la lámpara, you are switching on the actual lamp.
If you say enciendo la luz, you are talking more generally about turning the light on.

Both can be correct, but they are not exactly the same.

It is standard and helpful here because Cuando llego cansada is an introductory clause.

• Cuando llego cansada, dejo el llavero...

In Spanish, when a subordinate clause comes before the main clause, a comma is commonly used. It makes the sentence easier to read.

Yes, Spanish word order is fairly flexible, though some versions sound more natural than others.

For example, you could also say:

• Dejo el llavero en el recibidor y enciendo la lámpara del pasillo cuando llego cansada.

This is grammatically fine, but the original version feels more natural if you want to set the scene first: When I arrive tired...

So the original order is a very natural way to express it.