If the homicide was justifiable then no criminal act has been committed

The cast of Justifiable Homicide - 2010 includes: Herb Cremer as Herb Joseph Cremer as Joe

An example of justifiable homicide might be if you were attacked by someone and in fighting them off you killed them or somehow caused their death. Felonious homicide would be when you planned to kill someone, or your actions were such that death could be presumed to be the outcome.

I'm not familiar with the term "Excusable" Homicide. Justifiable Homicide occurs when it is ruled (usually a Grand Jury) that a death of someone was proper and occurred within the bounds of law (i.e.: the shooting death of an armed bank robber by a police officer).

Homicide is the killing of another person: straightforward. The degree of homicide can range from justifiable homicide to capital murder. This is all determined by the facts of the case.