divergence vs driftage

divergence and driftage both are nouns.

Word	Noun	Adjective	Verb	Adverb
divergence	Yes	No	No	No
driftage	Yes	No	No	No

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

divergence: a variation that deviates from the standard or norm
driftage: the deviation (by a vessel or aircraft) from its intended course due to drifting

Other hyponyms of divergence include discrepancy, variance, variant, flection, flexion, inflection.

divergence (noun)	driftage (noun)
the act of moving away in different direction from a common point	the deviation (by a vessel or aircraft) from its intended course due to drifting
a difference between conflicting facts or claims or opinions
an infinite series that has no limit
a variation that deviates from the standard or norm