1.

It was freezing cold, so I wore a thick coat.

2.

It snowed hard all night. As a result the airport was closed the following morning.

3.

We regret that you do not have the necessary qualifications, and therefore / consequently we are unable to offer you the job.

a.

So is the most common way of introducing a clause of result.

b.

As a result, therefore, and consequently (more formal than so) are often used at the beginning of a sentence or clause.

c.

When the marker is at the beginning of a clause, it is usually preceded by a comma, or comma + and.

d.

Therefore and consequently can also be used before a main verb, e.g. We have therefore / consequently decided not to offer you the job.

1.

I have stopped writing to her, because / as / since she never answers me.

2.

The plane was late because of the fog.

3.

Flight 341 has been delayed due to / owing to adverse weather conditions.

a.

Because, as, and since (more formal) are used to introduce clauses giving a reason and are synonyms. As is often used at the beginning of a sentence, e.g. As the weather is so awful, we've decided not to go out.

b.

Because of, due to, and owing to also express the reason for something. They are usually followed by a noun.

c.

Due to and owing to are more formal than because of.

1.

I did a language course in the United States to / in order to / so as to improve my English.

2.

She closed the door quietly so as not to / in order not to wake the baby.

3.

They moved to Mexico so (that) they could see their grandchildren more often.

4.

I'm not going to tell Ann in case she tells everyone else.

a.

To, in order to and so as to introduce a clause of purpose and are all followed by an infinitive. So as to and in order to are more formal.

b.

For negative purpose use in order not to or so as not to, NOT She closed the door quietly not to wake the baby.

c.

You can also use so (that) + can or could + verb or will I would + verb to express purpose. You can leave out that in informal speech and writing.

d.

You must use so (that) when there is a change of subject in the result clause, e.g. She put a rug over the baby so (that) he wouldn't be cold.

e.

Use in case + clause when we do something in order to be ready for future situations / problems or to avoid them.

1.

We enjoyed the concert, but we didn't have very good seats.

2.

Agnes was attracted to the stranger, yet something in her head was telling her not to get close to him.

3.

We enjoyed the concert. However, we didn't have very good seats.

4.

Agnes was attracted to the stranger. Nevertheless, something in her head was telling her not to get close to him.

5.

We enjoyed the concert although / even though / though we didn't have very good seats.

6.

In spite of being attracted to the stranger, something in Agnes's head was telling her not to get close to him.

7.

Despite her attraction to the stranger...

8.

Despite the fact that she was attracted to the stranger...

a.

But is the most common and informal way of introducing contrast, and is normally used to link two contrasting points within a sentence. Yet is used in the same way, but it is more formal / literary.
However and nevertheless are normally used at the beginning of a sentence, to connect it to the previous one. They are usually followed by a comma.

b.

Nevertheless (or nonetheless) is more formal / literary than however.

c.

Even though is more emphatic than although. Though is more common in informal speech. Though can also be used at the end of a phrase as a comment adverb, e.g. He's very friendly - a bit mean, though.

d.

After in spite of and despite you must use a gerund, a noun, or the fact that + clause.