WOULD, COULD, and SHOULD
Part I COULD
The dictionaries inform us that COULD shows "possibility"
or what can or could possibly be done.
"I could speak English if I was were <em>( see your later example, '... if you were a lawyer' but it is another topic)</em> willing to study."
"I could master the language if I studied with great effort."
"I could answer your question if I knew the answer."
When you think of COULD, think of it in terms of a specific SKILL or POTENTIAL you have to do something.
If you were a lawyer, you COULD represent someone in a court of law; but that does not mean that you would want to represent an evil criminal in a court of law.
If you were a Queen, you COULD order the execution of any citizen of your country without a trial; but that does not mean that you would want to order the execution of any citizen of your country.
If you found a man that you liked for a friend, you COULD date that man; but that does not mean that you would want to date every man that you liked for a friend.
If you were wealthy, you COULD enter into the manufacture of a line of custom made exotic sports cars that cost $500,000 each; but that does not mean that you would want to do that simply because you COULD do that.
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