The principal branch of an analytic multivalued function, also called a principal sheet, is a single-valued "slice" (i.e., branch) of the function chosen that is for convenience in referring to a specific canonical value (a so-called principal value) of the function for each complex z. For example, the principal branch of the natural logarithm, sometimes denoted Ln z, is the one for which ln1 = 0, and hence is equal to the value ln x for all x>0. The value of a function on its principal branch is known as its principal value.

branch | branch cut | branch point | Lambert W-function | multivalued function | principal value