A mistake in coding is called error,
when tester found that mistake during test executon then 
test engineers r callin defects  and when developers 
accepted that defects to solve ,we r calling as bug

Bug - An error, which involves coding is called bug.

Defect - A product or project which doesn't satisfies the 
requirement  is called defect.

Error - An Error occurs when the user does anything wrong 
((i.e)beyond the requirement) while using an application is 
called error.

Error- it occures in Coding part. Ex:Logical Errors.

Defect- mismatches between the Actual and Expected Results 
while testing are Defects.

Bug- If the defect is accepted by the developer after its 
called as Bug.

Error is an undesirable deviation from requirements

Bug is an error found BEFORE the application goes into 
production

Defect is an error found AFTER the application goes into 
production

Defect in the system if it does not work according to the 
SRS and FS.
Error is defect in documentation, defect in code, defect in 
application.
Bug is the error found in the system when working with the 
system.

error-mistakes made by the developer.

defect-error found by the tester in the software application.

bug-error found after the software application goes into 
production.

ERROR: A mistake happened in program which leads to
undesirable results.

BUG: An error which is found by the testers according to
client requirements during production process .

DEFECT:An error found after the production process which
tend to run the application in the unwanted manner.

ERROR : Takes place from the user's side 

As far as  bug and defect are concerned, these are 
different two terminologies used for the same thing.

So,

BUG or DEFECT: Takes place from the developers side

error : mostly syntactical... when u compile prog, it gives
u ERROR

bug : its logical.. DEBUG means finding bugs...

A mistake found by tester at the time of testing is know as
error

If that specific error is accepted by our developers then we
can cal it as defect/issue

If any mistake is found by the client after release of a
project then we can name it as bug which is can be accpected
by the developed project team