Difference between SOP and WI

Hi,
I really should know this now, but I have managed to confuse myself completely! (OK that does not take much at the best of times)

Can somebody please give me a concise definition of:
Work Instruction (WI's)
Standard Operating procedures (SOP's)
And specifically the difference- I think I have it sorted, but just want to know what everybody else's thinking is.

Thanks,
Regards,
Norah- Ann

Dear Norah-Ann,

I suspect the answer will depend on the choice of source / application. I enlarged yr question to include "Procedure".

Some options –

(1) Apparently ISO 9000 is vague on this (although from memory WI’s are always at the base of the “ISO Triangle”)
eg
Introduction
These are a few comments on the subject of the definition of ‘process’,
‘procedure’ and ‘work ‘instruction’.
Procedure vs work instruction
ISO 9000:2000 defines only two of the three terms (‘process’ and
‘procedure’). The new standards don’t define ‘work instruction’ (neither in
ISO 9000 nor in TC176’s subsequent Guidance on the Terminology used in
ISO 9001:2000 and ISO 9004:2000 – ISO/TC 176/SC 1/N 215 &
ISO/TC 176/SC 2/N 526R, May 2001).
‘Procedure’ is defined, in ISO 9000, as “a specified way to carry out an
activity or a process”. Sounds to me like that is very close to an
instruction to people on how to do their work! So I think the distinction
between a documented procedure and work instruction is, at best, very
slight.
ISO 9001 mentions ‘work instruction’ once (as an example of a controlled
condition in 7.5.1) but I reckon one could substitute ‘procedure’ for ‘work
instruction’ there without problem.
My view is that that you could consider simply dropping the distinction
between ‘procedure’ and ‘work instruction’.
However, if you do want to differentiate between the two types of
document, a good approach would be start with the customer and to
focus on the differences in terms of ‘purpose’ and ‘readership’. Ask “who
will use each type document and what, precisely, will they use it for?” The
answers will help to define the distinction – if any.
http://www.bin.co.uk/PPWI.pdf.

(2) On the other hand –

Procedure
A set of specific steps that describe how an activity should be carried out, and by whom. For example, the procedure dealing with carrying out a post-implementation review of a Change would be likely to describe the scope of the procedure (to what Changes does this procedure apply), its purpose and how the success of the Change will be measured, the individual procedural steps and the responsibilities for carrying out or being involved in each of those steps. Procedures may be supported by more detailed Work Instructions.
Work Instruction
A detailed set of instructions that describe exactly how a low-level activity must be carried out. For example, describing precisely how a RFC (Change) record is created in the Change Management software support tool. See also Procedure.
http://www.infodiv.u...ices/a-z/w.html

(3) and WI with respect to SOP -
• Work Instruction
Work Instructions are step-by-step instructions for the accomplishment of a task by one person and are retained in the department or unit where the work is performed. Work Instructions are often referred to as Desk Procedures, Task Outlines or SOPs (Standard Operating Procedures).
http://www2.slac.sta...definitions.asp

I think (2) and (3) are more typical but I must then have written many "WIs" which I called "Procedures". Additionally, I think "SOP" is often effectively elevated to the rank of "Procedure" as described in No.(2). If you decide based on "detail" the dividing line will surely be sometimes blurred.

What did you think the difference between "WI" and "SOP" is ?

Any more proposals ?

Rgds / Charles.C