A point charge is a hypothetical charge located at a single point in space.

summation (n.)
1760, "process of calculating a sum," from Modern Latin summationem (nominative summatio) "an adding up," noun of action from Late Latin summatus, past participle of summare "to sum up," from Latin summa (see sum (n.)). Meaning "a summing up" is from 1836.

summing-up; plural noun: summing-ups; plural noun: summings-up
a restatement of the main points of an argument, case, etc.
"he was obviously startled at her cynical summing-up of his offer"
LAW
a judge's review of evidence at the end of a case, with a direction to the jury regarding points of law.
"his summing-up left the jury in no doubt about his own views"

To give a brief and accurate summary, description, assessment, or representation of something; to summarize.

e quation; plural noun: equations

1.
MATHEMATICS
a statement that the values of two mathematical expressions are equal (indicated by the sign =).

Similar:
mathematical problem
sum