Bug is a condition which causes the s/w to fail.
eg:- programming errors, logical errors.

Defect is nonconfirmation with requirements i.e. it is the 
difference between expected output and acutal output.

eg:- if we perform an operation on the AUT we expect the 
output as "X" but the the operation results as "Y".
Here the expected value mismathes with actual value, so 
this nonconfirmation with requirement is calle defect.

Bug comes in coding whle debugging developers find the bug

 but while doing testing if any diff between actual result
and expected result it is called defect

Bugs & Defects meanings are changed with its location. 
Example.. If Developer is compiling a  Exe at that time any 
defects converted into Bug, But a tester find that bug 
converted into defects..

defect:-(eg)-consider ur launching a magazine.if the reader 
finds the mistakes in that, its called as Defect. 


another eg:ther is mistake in ur question (i.e diffect),
 as its spelling is 'defect'....



THIS IS CALLED AS DEFECT

normally a s/w tester cannot says bug,spells only 
diffect,because a tester's job is to find out the error,so 
he can't say bug

Error,bug,defect are given same menaing but  it will be 
used in different locations.When error will be get at the 
client location it is defect,if it arrises at tester place 
it is bug,if it will arises at developer place it is 
error,but all of the given same meaning that is expected 
behaviour of the application does not match with actual 
behaviour of the application.
 u have any qurriers contact with me.
 mail id :physics143@gmail.com

As per my view Bug and Defect are same thing. 

if u find the issue in production u may call it as defect.


if devloper find in dev env then they call it as bug

Bug and Defect are similar terms.
Bug is the word used by Tester when he finds the error
and defect is the word used by the Developer.

the error that was found in developement side  is called 
defect or issue.and that defect when comes testing side to 
resolve is called Bug

hi ramrao,anushree,satyaprasad all of you give wrong answer

BUG:WHEN TESTER FIND DIFFERENCE BETWEEN EXPECTED OUTPUT AND 
ACTUAL OUTPUT.
DEFECT:WHEN END USER REPORTS THE SAME THAT IS SAID TO BE 
DEFECT.

IN OTHER WORDS, BUG CAN BE RECTIFIED AT DEVELOPER SIDE 
BEFORE REALSING THE PRODUCT. DEFECT MAKE CUSTOMER 
DISSATISFIED. 

IF THERE IS DEFECT IN A PROJECT IT SHOWS THE POOR QUALITY 
OF TESTING.

Hi,
Defect-difference between actual result and excepted result
know as a defect.
Bug-does not meet the actual application exception result 
know as Bug.its ot we can say not fallow the correct process.