attachment vs welding

attachment and welding both are nouns.

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

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

attachment: the act of fastening things together
welding: fastening two pieces of metal together by softening with heat and applying pressure

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

attachment (noun)	welding (noun)
the act of fastening things together	fastening two pieces of metal together by softening with heat and applying pressure
the act of attaching or affixing something
faithful support for a cause or political party or religion
a supplementary part or accessory
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