alluvium vs alluvion

alluvium and alluvion both are nouns.

Word	Noun	Adjective	Verb	Adverb
alluvium	Yes	No	No	No
alluvion	Yes	No	No	No

As nouns, alluvium and alluvion are synonyms defined as:

alluvium and alluvion: clay or silt or gravel carried by rushing streams and deposited where the stream slows down

Other synonyms of alluvium include alluvial deposit, alluvial sediment.

alluvium (noun)	alluvion (noun)
clay or silt or gravel carried by rushing streams and deposited where the stream slows down	clay or silt or gravel carried by rushing streams and deposited where the stream slows down
	the rising of a body of water and its overflowing onto normally dry land
	gradual formation of new land, by recession of the sea or deposit of sediment