Lethal, Fatal or Deadly?

As 2014 is preparing to pass from existence, I thought about the various synonyms for deadly and the gradations between them.

Are lethal and fatal the same? What about mortal? Or terminal? Deadly?

Although the words are close in definition, there are distinctions. If a weapon is lethal, it is capable of inflicting death. If it is fatal, it has been successful. The fatal blow is the killer. If the blow is only lethal, the victim might yet survive. Mortal means nearly the same as lethal, destruct...