What is the difference between a full brother and a half-brother in the distribution of inheritance?

A half-brother is either a maternal half-brother (akha li-umm), who is a sharer (sahib fard). He inherits one-sixth if he is alone, and one-third if there are multiple maternal half-siblings. He does not inherit in the presence of male or female lineal descendants, or a male lineal ascendant. Or he is a paternal half-brother (akha li-ab), who is one of the 'asabah (agnatic heirs). He is excluded by a full brother, and takes his place in his absence.