invasion vs encroachment

invasion and encroachment both are nouns.

Word	Noun	Adjective	Verb	Adverb
invasion	Yes	No	No	No
encroachment	Yes	No	No	No

As nouns, invasion and encroachment are synonyms defined as:

invasion and encroachment: any entry into an area not previously occupied

Other synonyms of invasion include intrusion.

invasion (noun)	encroachment (noun)
the act of invading; the act of an army that invades for conquest or plunder	entry to another's property without right or permission
any entry into an area not previously occupied	influencing strongly
(pathology) the spread of pathogenic microorganisms or malignant cells to new sites in the body	any entry into an area not previously occupied