The difference between Gist and Sum

When used as nouns, gist means the most essential part, whereas sum means a quantity obtained by addition or aggregation.

When used as verbs, gist means to summarize, to extract and present the most important parts of, whereas sum means to add together.

check bellow for the other definitions of Gist and Sum

Gist as a noun:

The most essential part; the main idea or substance (of a longer or more complicated matter); the crux of a matter; the pith.
Gist as a noun (legal, dated):

The essential ground for action in a suit, without which there is no cause of action.
Gist as a noun (obsolete):

Resting place (especially of animals), lodging.

Gist as a verb:

To summarize, to extract and present the most important parts of.

Sum as a noun:

A quantity obtained by addition or aggregation.

Examples:

"The sum of 3 and 4 is 7."
Sum as a noun (often plural):

An arithmetic computation, especially one posed to a student as an exercise (not necessarily limited to addition).

Examples:

"We're learning about division, and the sums are tricky."
Sum as a noun:

A quantity of money.

Examples:

"a tidy sum"

"the sum of forty pounds"
Sum as a noun:

A summary; the principal points or thoughts when viewed together; the amount; the substance; compendium.

Examples:

"This is the sum of all the evidence in the case."

"This is the sum and substance of his objections."
Sum as a noun:

A central idea or point.
Sum as a noun:

The utmost degree.
Sum as a noun (obsolete):

An old English measure of corn equal to the quarter.