Using si / sí for emphasis in Spanish

The words si and sí are often used colloquially in Spanish to add some kind of emphasis in different contexts. Sometimes they are part of a specific phrase. 

Let's see the most common uses of si and sí with this emphatic functionality.

si... / pero si... / si es que... (enfático)

Both si...and pero si...  followed by a sentence are often used when a person wants to show surprise, protest, objection or justification towards something that has been said.

For example, if someone says:

The other person (the accused one) may reply this way towards that statement:

The message behind that si / pero si is "what are you talking about?", "I can't believe what you're saying!", "that's so unfair!

Depending on each context it will take one meaning or another. Sometimes it's a very light surprise, protest, objection or justification, and sometimes it has more weight. 

Some other examples are:

Sometimes and with the same meaning and probably even more emphatic, si can be followed by "es que": si es que...

For example:

Replying to this statement:

Someone could emphasise this statement by reinforcing the idea of lack of safety by saying for example:

With "si es que..." we make a point. It emphasises the statement, adding an idea to reinforce it.

It's important to bear in mind that the phrase "si es que" can also have a conditional functionality (if), in which case it has a completely different meaning. It's necessary to read the context to know the difference. For example:

sí..., sí que... (enfático)

With sí with an accent and often followed by que... we reaffirm something; it's similar to the effect of "indeed, actually" or the equivalent to reinforcing the verb with the auxiliary "do", "did"... in English. 

For example: