What is second normal form in DBMS?

Second normal form is valid in a table which have composite primary key which is made with the combination of two columns.So if we have A,B,C,D,E attributes in our table and C,D are fully functional dependent on A,B.But E is partially functional dependent on A,B,Mean if we use Only B to define E coloumn then that will be suffecent.so then we use 2nd normal form & we create two tables with coloumns attributes A,B,C,D and the other table with coloumns attribute B,E.That will be called second normal form.