Consider the following three sentences:

1. If I had the money, I would get the operation.
2. If only I had the money, I would get the operation.
3. I would get the operation only if I had the money.

• The first expresses a simple failed conditional. I don't have the money, but if I did, I would get the operation.
• The second expresses a failed conditional with greater emotional content. I don't have the money, but if I did, I would get the operation and it really bothers me.
• The third expresses a failed conditional, without the emotional content, but with a greater stress on the monetary constraint.