I am reading basic sets. In the section of sesquilinear mapping, I came across this mapping $f: X \to X^*$ i.e $x \ $ maps to $ (x|.)$
Here I know $X$ is a function space, I guess $X^*$ stands for its dual. $(|)$ is inner mapping.
My question: What exactly is $(x|.)$?
Thanks in advance for the explanation.