The word "ethics" comes from the Greek word ēthikós (ethical) and êthos (character), and the Latin ethice.   Its origins relate to custom, habit, and character, meaning the study of morals or character.  The term is strongly associated with Aristotle's work, Ta Ethika (The Ethics), which focused on moral philosophy. 

The noun "ethics" was first used in English during the Middle English period, with the Oxford English Dictionary finding evidence from before 1425. The word traces back to the Middle English term "ethik" and was partly borrowed from the Old French "éthique" and Latin "ethica". The noun "ethics," was specifically used to refer to "the science of morals" around 1600.  The singular noun ethic is from before 1387, in a translation by John Trevisa.   The English word "moral" also has a related root, coming from the Latin mores, meaning "customs". 

To be ethical means to act in a way that aligns with moral principles, focusing on what is right, fair, and honest, even when no one is watching.  It involves making decisions based on values like integrity, respect, and responsibility, and is guided by both personal beliefs and societal standards. While laws tell you what you must do, ethics guide what you should do. 

Examples of "ethic" used in a sentence:  
"But a strong work ethic was instilled in him at an early age." 
"I loved their work ethic and determination." 
"I know the determination and work ethic he has always had to make sure he does the job right."
"The reality is that democracy prefers to adopt its own ethic." 

Examples of "ethics" used in a sentence: 
"We set up the ethics committee with two chambers." 
"Its members are bound by a rigid code of ethics which includes confidentiality." 
"Refugee workers said such action was a violation of medical ethics."
"It is common to distinguish between personal and social ethics."
"He told the police that he had thought honestly about the ethics of what he was doing." 

 Just the facts:

ETHICS Definition & Meaning | Merriam-Webster Legal

ETHICS Synonyms: 16 Similar Words | Merriam-Webster Thesaurus

CODE OF ETHICS Definition & Meaning - Merriam-Webster

WORK ETHIC Definition & Meaning - Merriam-Webster

13 hours ago, drpaladin said:

It's surprising ethics are considered an important part of the study of law after you've had the dubious pleasure to know some lawyers. 

9 hours ago, Myr said:

They all study it so as to know what they need to avoid doing. 😛 

Good theories.  I have met a few lawyers, however, who seem to have studied ethics so they can try to make some of their legal maneuvers LOOK ethical.  The majority of lawyers I have met, however, mean well.