The difference between Addition and Inclusion

When used as nouns, addition means the act of adding anything, whereas inclusion means an addition or annex to a group, set, or total.

check bellow for the other definitions of Addition and Inclusion

Addition as a noun (uncountable):

The act of adding anything.

Examples:

"The addition of five more items to the agenda will make the meeting unbearably long."
Addition as a noun:

Anything that is added.
Addition as a noun (uncountable):

The arithmetic operation of adding.
Addition as a noun (music):

A dot at the right side of a note as an indication that its sound is to be lengthened one half.
Addition as a noun (chiefly, legal):

A title annexed to a person's name to identify him or her more precisely, as in "John Doe, Esq.", "Robert Dale, Mason", "Thomas Way, of New York".
Addition as a noun (heraldry):

Something added to a coat of arms, as a mark of honour; opposed to .

Inclusion as a noun (countable):

An addition or annex to a group, set, or total.

Examples:

"The poem was a new inclusion in the textbook."
Inclusion as a noun (uncountable):

The act of including, i.e. adding or annexing, (something) to a group, set, or total.

Examples:

"The inclusion of the poem added value to the course."
Inclusion as a noun (countable):

Anything foreign that is included in a material,
Inclusion as a noun (countable, mineralogy):

Any material that is trapped inside a mineral during its formation, as a defect in a precious stone.
Inclusion as a noun (biology):

A nuclear or cytoplasmic aggregate of stainable substances.
Inclusion as a noun (mathematics):

A mapping where the domain is a subset of the image.