How to rename standard fields in salesforce

Example :To rename "Account Name" field of Account as Customer Name
Steps:
Step 1:Go to Setup --> Build --> Customize --> Tab Names and Labels --> Click on "Rename Tabs and Labels".

Step 2: Click on edit next to concerned object.In this case click on Edit before Account object.

Step 3:Click on Next.The following Screen appears.Rename the concerned field in Singular column as shown in image below.

and then click on "Save".
Label before rename looks like this

Label after rename looks like this