filler vs sizing

filler and sizing both are nouns.

Word	Noun	Adjective	Verb	Adverb
filler	Yes	No	No	No
sizing	Yes	No	No	No

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

filler: used for filling cracks or holes in a surface
sizing: any glutinous material used to fill pores in surfaces or to stiffen fabrics

Other hyponyms of filler include putty, mastic, size, stiffener.

filler (noun)	sizing (noun)
the tobacco used to form the core of a cigar	any glutinous material used to fill pores in surfaces or to stiffen fabrics
anything added to fill out a whole
copy to fill space between more important articles in the layout of a magazine or newspaper
100 filler equal 1 forint in Hungary
used for filling cracks or holes in a surface