Conjunciones

And

I study and my brother watches TV

As (mientras; la 2° acción ocurre antes de que la 1° haya finalizado, o evolucionan paralelamente)

As he grew older he became more aggressive

Because (porque)

You cannot go to the party because you are too young

Both ... and

Both the Spanish team and the English one play football quite well

But

I studied very hard but I didn't pass the exam

Either ... or

I have to decide to go either to Paris or to London

However (como quiera, sin embargo)

I explained my problem to him, however he didn't understand it

If (si -condicional-)

If he studys he will pas his exams

Neither ... nor

I like neither this tie nor that one

Nevertheless (sin embargo)

I didn't receive an invitation to the party; nevertheless I went there

Not only ... but also

My brother not only speaks French but also German

Or

From here to Gibraltar you can go by train or by car

Otherwise (de otro modo)

We must leave now, otherwise we will lose our flight

So (por lo tanto)

It was raining a lot, so we decided to rest at home

That (que)

I didn't know that you had bought a new car

Therefore (mismo significado que "so" pero más formal)

I had fever; therefore I didn't go to work

Though (aunque, pero) ("Although" tiene el mismo significado pero es más formal)

He didn't admit his fault, though he knew it was his responsibility

Unless (a menos que)

Unless you study more you won´t pass your exams

When (cuando; las dos oraciones ocurren simultáneamente o una detrás de la otra)

When the weather is good lots of people go to the beach

Diferencia entre When / as

Las 2 se utilizan para acciones paralelas.

La conjunción "when" también se utiliza cuando una acción ocurre después de la otra:

When you finish your homework you will play with your friends

"As" también se emplea cuando una acción ocurre antes que finalice la otra

As I flew to Barcelona I started feeling bad

While (mientras)

While I was away my house was burgled