The difference between Abridgment and Compendium

When used as nouns, abridgment means the act of abridging, whereas compendium means a short, complete summary.

check bellow for the other definitions of Abridgment and Compendium

Abridgment as a noun (US):

The act of abridging; reduction or deprivation

Examples:

"synonyms: diminution lessening shortening<ref name=SOED/>"

"an abridgment of pleasures or of expenses"
Abridgment as a noun (US):

The state of being abridged or lessened.
Abridgment as a noun (US):

An epitome or compend, as of a book; a shortened or abridged form; an abbreviation.
Abridgment as a noun (obsolete):

That which abridges or cuts short; hence, an entertainment that makes the time pass quickly
Abridgment as a noun (dated, legal):

Any of various brief statements of case law made before modern reporting of legal cases.
Abridgment as a noun (legal):

The leaving out of certain portions of a plaintiff's demand, the writ still holding good for the remainder.

Compendium as a noun:

A short, complete summary; an abstract.
Compendium as a noun (pharmaceutical industry):

A list or collection of various items. A collection of board games packaged in a single box. A collected body of information on the standards of strength, purity, and quality of drugs.