Plural of oligohalino, derived from the Greek adjective: oligos oligon olige: little and hals halos: salt, sea ( haline haline halinon: saline, marine ): has little salt ( sodium chloride: NaCl ). The salinity of the water is from the end of the 20th century, expressed in grams per litre. Less than half a gram per litre is considered fresh water. Of half a gram to 30 grams, brackish water. 30 to 50 grams, seawater and more than 50 grams, brine. Water that contains less than 50 grams per litre is considered oligohalina.