briny vs brackish

briny is a noun but brackish is not a noun.

Word	Noun	Adjective	Verb	Adverb
briny	Yes	Yes	No	No
brackish	No	Yes	No	No

As adjectives, briny and brackish are synonyms defined as:

briny and brackish: slightly salty (especially from containing a mixture of seawater and fresh water)

briny (noun)	brackish (noun)
any very large body of (salt) water

briny (adjective)	brackish (adjective)
slightly salty (especially from containing a mixture of seawater and fresh water)	slightly salty (especially from containing a mixture of seawater and fresh water)
	distasteful and unpleasant; spoiled by mixture