pillar vs piling

pillar and piling both are nouns.

Word	Noun	Adjective	Verb	Adverb
pillar	Yes	No	No	No
piling	Yes	No	No	No

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

pillar: (architecture) a tall vertical cylindrical structure standing upright and used to support a structure
piling: a column of wood or steel or concrete that is driven into the ground to provide support for a structure

Other hyponyms of pillar include atlas, telamon, caryatid, newel, pilaster, pile, spile, stilt, support column.

pillar (noun)	piling (noun)
(architecture) a tall vertical cylindrical structure standing upright and used to support a structure	a column of wood or steel or concrete that is driven into the ground to provide support for a structure
a vertical cylindrical structure standing alone and not supporting anything (such as a monument)
a fundamental principle or practice
a prominent supporter
anything that approximates the shape of a column or tower