defect:while Executing any build if testing people found 
that expected is not equal to actual then it is known as 
defecf.

Bug:when developers are accepting it as defect then it is 
known as bug.

Error:Error is a syntax Error by the developers

Fault:A fault in a program which causes the program to 
perform in an unintended or unanticipated form

Bug is Problem in code

Defect is Variance between expected and actual

bug is a incorrect step , process or data definition in a
computer program.

Bug: when developers are accepted it then it is 
Known as bug.

Error: Error is a syntax Error It will appears only at 
White Box testing.

Fault: A fault in a program, which causes the program to 
perform in an unintended or unanticipated form.

Defect: Defect is nothing but deviation from the client 
requirements. Nothing but which is not presented in the SRS 
(Software Requirements Specifications.) Document.

Feel free to ask questions. 

My Mail Id penisetty@Gmail.com

Defect-- deviation from expected, or difference between 
expected result & actual result.

failure--manifestation of fault

bug--software doesn't do something that the product 
specification says it should do.

error--undesired step or procedure

Error is the terminology used in programming which can be
two types logical and syntax.

Defect or Bug or Fault is any deviation from the requirement
can be call as Defect or Bug or Fault.Failure is inability
of the system to perform a task on a given condition 
Defects are reported when the expected result is not
matching with actual result,defects are reported to test
engineer for every test cases we fail we need to report a
defect.For a single test case we can have multiple defects

if any mistake in my answer plzzzzzzzz mail mee
sridharraghava@gmail.com

Error :It comes from the Programmers side i,e the error
either syntically or else in logic...
Bug: It comes from testing side when a tester found that the
expected is not same as the actual....
Defact: after launching the software if any mishaps coming
from the Clietside then its a defact...