El cepillo está mojado, así que lo dejo junto al lavabo mientras busco el secador.

Because Spanish uses estar for a temporary state or condition, and being wet is usually temporary.

• está mojado = it is wet right now
• es mojado would sound strange in most situations, because it suggests that being wet is an essential or permanent characteristic

So here estar is the natural choice.

Because mojado agrees with el cepillo, which is masculine singular.

In Spanish, adjectives usually match the noun in gender and number:

• el cepillo mojado = masculine singular
• la toalla mojada = feminine singular
• los cepillos mojados = masculine plural
• las toallas mojadas = feminine plural

Since cepillo is masculine singular, mojado has to be masculine singular too.

Así que means so, therefore, or so then. It introduces a result or consequence.

Here the logic is:

• El cepillo está mojado = the brush is wet
• así que lo dejo junto al lavabo = so I leave it next to the sink

A useful comparison:

• porque = because → gives the reason
• así que = so → gives the result

For example:

• Lo dejo junto al lavabo porque está mojado. = I leave it next to the sink because it’s wet.
• Está mojado, así que lo dejo junto al lavabo. = It’s wet, so I leave it next to the sink.

Lo is a direct object pronoun meaning it. It refers back to el cepillo.

So:

• el cepillo = the brush
• lo dejo = I leave it

Because cepillo is masculine singular, the pronoun is lo.

Compare:

• el cepillo → lo
• la toalla → la
• los cepillos → los
• las toallas → las

In Spanish, object pronouns normally go before a conjugated verb.

So you say:

• lo dejo
• la busco
• los encuentro

Not:

• dejo lo

However, with an infinitive, gerund, or affirmative command, pronouns can attach to the end:

• voy a dejarlo
• estoy buscándolo
• déjalo

But in lo dejo, the normal position is before the conjugated verb.

Spanish often uses the simple present where English prefers the present continuous.

So:

• lo dejo can mean I leave it or I’m leaving it
• busco can mean I look for or I’m looking for

In this sentence, the present tense describes what the speaker is doing at that moment. This is completely natural in Spanish.

If you wanted to be more explicit about the ongoing action, you could say:

• lo estoy dejando
• estoy buscando el secador

But the simple present is usually the most natural choice here.

Because Spanish often drops subject pronouns when they are already clear from the verb ending.

• dejo = I leave
• busco = I look for

The -o ending already tells you the subject is yo, so saying yo is not necessary.

You could say yo dejo or yo busco, but it would usually add emphasis or contrast, for example:

• Yo lo dejo aquí, pero tú llévatelo luego.

In a normal sentence like this, leaving out yo is standard.

Junto a means next to, beside, or right by.

So:

• junto al lavabo = next to the sink

It suggests closeness. Very often, junto a is used just like English next to.

Examples:

• junto a la puerta = next to the door
• junto al espejo = next to the mirror

Because a + el contracts to al in Spanish.

So:

• a + el lavabo → al lavabo

This contraction is mandatory.

The same thing happens with de + el:

• de + el baño → del baño

But note that this only happens with el, not with la:

• junto a la puerta (not contracted)

In Spain, lavabo commonly means sink or washbasin.

Depending on context, it can sometimes also refer to a toilet/washroom, but in this sentence junto al lavabo clearly means next to the sink.

A learner should not confuse it with:

• baño = bathroom
• ducha = shower
• fregadero = kitchen sink

In this sentence, lavabo fits a bathroom setting.

Mientras means while.

It introduces another action happening at the same time:

• lo dejo junto al lavabo = I leave it next to the sink
• mientras busco el secador = while I look for the hairdryer

Both verbs are in the present because both actions are happening in the same general moment.

In English, you might say:

• while I look for the hairdryer
• while I’m looking for the hairdryer

Spanish busco can cover both ideas here.

Yes. In Spain, secador often means hairdryer, especially in a bathroom context.

The full expression is:

• secador de pelo = hairdryer

But very often, Spanish speakers just say secador when the meaning is obvious.

So here el secador is most naturally understood as the hairdryer.

Spanish often uses the definite article more than English does.

In this sentence, the speaker is talking about specific, identifiable things:

• el cepillo = the brush already being discussed
• el lavabo = the sink in that setting
• el secador = the dryer the speaker is trying to find

English sometimes omits articles in places where Spanish keeps them, but here all three definite articles sound natural in Spanish.

Not by itself. Cepillo is a general word meaning brush, so the exact type depends on context.

It could be, for example:

• a hairbrush
• a clothes brush
• a toothbrush, in some contexts

If Spanish needs to be more specific, it can say:

• cepillo de pelo = hairbrush
• cepillo de dientes = toothbrush

So el cepillo here just means the brush, and the context tells you what kind it probably is.