Reason that / reason why

Reason can be followed by why… or that… Because is not possible in this case.

• The reason why he lost his job was that he was dishonest. (NOT The reason because he lost …)
• The reason why she didn’t come was that her mother was ill.
• The reason that she doesn’t like you is that you criticize her all the time.

That / why can be dropped in an informal style.

• The reason (that) I am asking is that I desperately need some money.

Because and in order that

Use because to show reason. Use in order that to show purpose.

• He was absent because he was ill.
• We send them weekly reports in order that they will have all the information they need.

So that means the same as in order that. It is more common in an informal style.

• We eat so that we may live.

Such …that

Structures with very cannot be followed directly by that-clauses. Instead, we use such…that

• It was such a cold afternoon that we stopped playing. (NOT It was a very cold afternoon that we stopped playing.)

Such as

Such as is used with nouns to introduce examples.

• In such areas as Karnataka and Rajasthan, there are many historical monuments and ruins.
• The doctor has advised me to avoid fatty foods such as cakes and pizzas.

Note that such as cannot be followed by a clause.