What's the difference between a soldier, an assassin, and a mercenary?

[GoldenRivet]

SOLDIER: a professional, similar to a police officer, who is instilled with principles like Duty, loyalty, patriotism and Honor. He protects individuals of a sovereign nation from the aggression of foreign attack. he is paid to do more than "kill". he also is paid to builds bridges where there are none, he may shores up a swelling river when a town is in danger of flooding, he helps to evacuate or rescue the captive or stranded, he serves his community and helps inspire the principles of patriotism, duty and honor in others.

ASSASSIN: An individual - perhaps a professional - perhaps not; who, for their own personal political gains or the political gains of a group or nation murders a public figure such as a president, king, ambassador, etc. an assassin is not necessarily always facing monetary gain in performing this task.

MERCENARY: an individual or a group of individuals who fights for personal monetary gain only. This person does not genuinely care about the cause of his employer. he does not care whether his employer is a mass murdering genocidal fascist, nor does he care if his employer is a righteous nation seeking to liberate a neighboring nation of a dictator's reign. He does not care whether his employers motives for military action are good or evil; nor does he care who the "enemy" he kills might be... his only motivation is to work for whoever is willing to pay the most money.