implemented using objects requires hash function, might have collisions worst time: search, insertion, deletion: o(n); linear; fair worst space: o(n); linear; fair
implemented using objects requires hash function, might have collisions worst time: search, insertion, deletion: o(n); linear; fair worst space: o(n); linear; fair
-associate key to record with hash function -applies to more than one attribute -good for looking up values based on equality -cannot answer range based queries