No cuelgues la camisa en el tendedero hasta que deje de llover.

Because this is a negative command addressed to tú.

In Spanish:

• affirmative tú command: cuelga
• negative tú command: no cuelgues

Negative commands for tú use the present subjunctive, not the regular imperative form.

It comes from the verb colgar = to hang.

This verb has a stem change o → ue in many present-tense forms:

• yo cuelgo
• tú cuelgas

Since negative tú commands use the subjunctive, you get:

• no cuelgues

So cuelgues is the subjunctive form of colgar for tú.

Because Spanish usually leaves out subject pronouns when they are obvious from the verb ending.

No cuelgues already tells you the subject is tú, so adding tú is not necessary.

You could say Tú no cuelgues la camisa..., but that sounds more emphatic, as if you are contrasting with someone else or stressing the instruction.

In Spain, tendedero usually means a clothesline, drying rack, or the place where clothes are hung to dry.

It can refer to:

• an outdoor clothesline
• an indoor drying rack
• a fixed area for hanging laundry

It is a very common word in Spain Spanish.

Because Spanish normally says colgar algo en a place where it will hang.

So:

• colgar la camisa en el tendedero = to hang the shirt on the clothesline / drying rack

Using en here marks the location where the shirt is placed.

Because hasta que often takes the subjunctive when the action is still in the future or has not happened yet.

Here, the rain has not stopped yet, so Spanish uses:

• hasta que deje de llover

Compare:

• future/unrealized: Espera hasta que deje de llover
• completed past event: Esperé hasta que dejó de llover

So deje is subjunctive because the stopping of the rain is still pending.

Spanish does not use a dummy subject like English it with weather expressions.

English says:

• until it stops raining

Spanish simply says:

• hasta que deje de llover

There is no need for a word equivalent to English it here.

Dejar de + infinitive is a fixed Spanish structure meaning to stop + -ing or to stop doing something.

So:

• dejar de llover = to stop raining
• dejar de hablar = to stop talking
• dejar de fumar = to stop smoking

The de is part of the expression, so you should learn it as a whole:

• dejar de + infinitive

La camisa suggests a specific shirt that both speaker and listener can identify from the context.

So:

• la camisa = the shirt
• una camisa = a shirt / one shirt

Here, the sentence sounds like it is talking about a particular shirt, not just any shirt.

Not always.

Camisa usually means a shirt, especially a more standard shirt such as a button-up or collared shirt.

If you mean a T-shirt, Spanish usually says:

• camiseta

So English shirt can correspond to different Spanish words depending on the type.

Sometimes, yes, but the meaning shifts slightly.

• colgar = to hang
• tender la ropa = to hang out the laundry / put washing out to dry

In Spain, tender is very common when talking about laundry in general:

• No tiendas la ropa hasta que deje de llover

But with a single item like la camisa, colgar is very natural and straightforward.

You change the command form:

• tú: No cuelgues la camisa en el tendedero hasta que deje de llover.
• usted: No cuelgue la camisa en el tendedero hasta que deje de llover.
• vosotros: No colguéis la camisa en el tendedero hasta que deje de llover.
• ustedes: No cuelguen la camisa en el tendedero hasta que deje de llover.

The rest of the sentence stays the same.