What is the difference between "an act of terrorism", "act of war" and "murder committed by someone with a mental illness"?

Syria kills people which it thinks are terrorists, with chemical weapons - enemies of a its democracy. The USA kills people, it thinks are terrorists - enemies of democracy - and now this includes Syria (or does it?) And Canada, apparently, thinks it is okay to kill people who kill others using chemical weapons. No need to argue about "complicity" - Canada is in favour of it Will it drop bombs too?.

 When Syria kills people with chemical weapons and when the USA kills people with cruise missiles - are any of theses "acts of terrorism ?". When does a cluster of "acts of terrorism" (suicide bombers) become the basis for acts of war ?  When will western style democracies stop saying "act of terrorism" and call it act of war?

Too many people are murdered in the world on a daily basis.In the USA 100's of people are murdered every day ... what are these acts called?