attachment vs linkage

attachment and linkage both are nouns.

Word	Noun	Adjective	Verb	Adverb
attachment	Yes	No	No	No
linkage	Yes	No	No	No

As nouns, linkage is a hyponym of attachment; that is, linkage is a word with a more specific, narrower meaning than attachment:

Other hyponyms of attachment include bonding, soldering, doweling, earthing, grounding, ligature, tying, welding, fixation.

attachment (noun)	linkage (noun)
the act of fastening things together	the act of linking things together
the act of attaching or affixing something	a mechanical system of rods or springs or pivots that transmits power or motion
faithful support for a cause or political party or religion	(genetics) traits that tend to be inherited together as a consequence of an association between their genes; all of the genes of a given chromosome are linked (where one goes they all go)
a supplementary part or accessory	an associative relation
a connection that fastens things together
a writ authorizing the seizure of property that may be needed for the payment of a judgment in a judicial proceeding
a feeling of affection for a person or an institution