5 = 5 + 0i
The definition of a prime number is a number that is dividible by 1 and itself, so it has only two factors. 1 has only one factor, so it does not fit the definition of a prime number.
The definition is yours to choose as you see fit.
If most of them lie below the line, then that line isn't the best fit. The exact layout depends on what definition you use for "best fit", but any definition will produce a line that has roughly the same number of data points on each side of it.
Yes, Panama fits the definition of an isthmus.
Yes it is a real number. Real numbers exist on a number line, so it doesn't matter big they are, they will always fit. Complex numbers on the other hand will never have a place on that number line.
"Living in water" IS the definition. You are looking for a word to fit that definition. Aquatic is probably what you are looking for.
Clean, fit, and proper.
yes
Hi
No, not everything that can be seen fits the definition of matter. Matter refers to physical substances that occupy space and have mass. Some things that can be seen, such as light or energy, do not fit this definition.
"Good Samaritanism" or "volunteerism" fit the definition.
The formal definition of a rational number is: Any number that can be written as a fraction with whole numbers on top and bottom. 3/4 certainly seems to fit that description.