Third Normal Form

Prior to Normalization

Item	Colors	Price	Tax
Pen	red, blue	2.0	0.20
Scale	red, yellow	2.0	0.20
Pen	red, blue	2.0	0.20
Bag	blue, black	150.00	7.80

This table is not in first normal form because :
  A. There are multiple fields in color lab.
  B. Records are repeating (Duplicate records) or no primary key.

First Normal Form (1NF)

Item	Colors	Price	Tax
Pen	red	2.0	0.20
Pen	blue	2.0	0.20
Scale	red	2.0	0.20
Scale	yellow	2.0	0.20
Bag	blue	150.00	7.80
Bag	black	150.00	7.80

This table is now in first normal form.

Second Normal Form (2NF)
The concept of remove the delicacy of data comes in the Second Normal Form (2NF).

A.  It should meet all the requirements of the first normal form.
B.  It should remove subsets of data that apply to multiple rows of a table and place them in separate tables.
C.  It create relationships between these new tables and their predecessors through the use of foreign keys. 

The First Normal form deals with the atomicity whereas the Second Normal Form deals with the relationship between the composite key columns and non-key columns. To achieve the next progressive level your table should satisfy the requirement of First Normal Form then move towards the Second Normal Form.
Let's introduce a Review table as an example :

Item	Colors	Price	Tax
Pen	red	2.0	0.20
Pen	blue	2.0	0.20
Scale	red	2.0	0.20
Scale	yellow	2.0	0.20
Bag	blue	150.00	7.80
Bag	black	150.00	7.80

Table is not in Second Normal Form because the price and tax depends on the item, but not color.

Item	Colors
Pen	red
Pen	blue
Scale	red
Scale	yellow
Bag	blue
Bag	black

Item	Price	Tax
Pen	2.0	0.20
Scale	2.0	0.20
Bag	150.00	7.80

Tables are now in Second Normal Form.


Third Normal Form (1NF)
The Third Normal Form has one more additional requirement :
        A. It should meet all the requirements of the second normal form.
      B. It should remove columns that are not dependent upon the primary key.
In the Third Normal Form all columns depend upon the primary key. When one column depends upon the other column,  table break the rule and turns into the dependency on the primary key.      

Item	Colors
Pen	red
Pen	blue
Scale	red
Scale	yellow
Bag	blue
Bag	black

Item	Price	Tax
Pen	2.0	0.20
Scale	2.0	0.20
Bag	150.00	7.80

Tables are not in Second Normal Form because tax depends on price, not item.
Tables are now in Third Normal Form with tables

Item	Colors
Pen	red
Pen	blue
Scale	red
Scale	yellow
Bag	blue
Bag	black

Item	Price
Pen	2.0
Scale	2.0
Bag	150.00

Price	Tax
2.0	0.20
150.00	7.80