1. The jury is made up of 12 civil people.
2. A jury is composed of 12 common people.
3. There were two juries in the court.
(Are the sentences correct? Do I have to use 'a jury' or 'the jury'? Is #3 correct?)
Not all juries consist of 12 people. So 2) is wrong.
1, and 3 are correct, The use of civil is odd. I am not certain how one determines 12 people are civil, unless you know them an extended time.
For #1, I'd say, "The jury is made up of 12 people." (You don't need the word "civil" in there!!)
1. The sentence "The jury is made up of 12 civil people" is correct grammatically, but may not be the most commonly used phrase. It could be rephrased to say "The jury is composed of 12 members of the public" or "The jury consists of 12 regular citizens."
2. The sentence "A jury is composed of 12 common people" is also grammatically correct. However, the word "common" may not be the most appropriate term to describe the members of a jury. It would be more appropriate to say "A jury is composed of 12 ordinary citizens" or "A jury consists of 12 laypersons."
3. The sentence "There were two juries in the court" is grammatically correct, but it doesn't provide any additional information about the juries themselves. If you want to be more specific, you could say "There were two separate juries in the court" or "There were two juries present for different cases in the court."
As for the use of "a jury" versus "the jury," it depends on the context. "A jury" is used when referring to any jury in general or when introducing a specific jury for the first time. "The jury" is used when referring to a specific jury that has already been mentioned or is known in the context.
For example, if you are talking about a jury in a specific court case, you would initially say "The jury in this case..." and subsequently refer to it as "the jury." If you are discussing juries in general, you would say "A jury consists of..." or "In a court of law, a jury is responsible for..."
Regarding sentence #3, it is important to clarify what you mean by "two juries." Typically, there is one jury for each court case. If you are referring to multiple court cases happening simultaneously, then it is possible to have multiple juries present. However, this is not a common occurrence. It would be more common to say "There were multiple court cases in session" or "There were two cases being heard in the court."