RIF -- for reduction in force -- is becoming a household word in government as the bureaucracy ponders President Reagan's proposed cuts in federal spending, programs and jobs. The size of the coming RIF is not yet know. Most federal officials think it will be August before any major layoffs are made. But agencies are working on RIF plans in case they must make cuts that cannot be met by attrition.

A RIF, to the typical civil servant, is something like a tornado: You know vaguely what it is, and you know you don't want to go through one. But few people are sure how the thing operates.

To answer some of the things you wanted to know, but were afraid to ask, Uncle Sam has updated a pamphlet of RIFs. It is called Fed Facts No. 13 (that number is coincidence, officials say). Anybody in an agency facing a possible RIF ought to study the phamplet. It explains what a RIF is, and how it is supposed to work.

During a RIF, workers can be forced to move to another job or a lower-grade job, or they can be fired or furlonged. More senior people can and do "bump" less senior workers, often into the street.

Federal agencies can decide which functions -- and jobs -- are to be abolished should a RIF become necessary. Once agencies make a RIF determination, they are supposed to give 30 days' notice before any action take place. Some terms you need to know:

Comptitive AREA -- This is a geographic and organizational area set up for RIF purposes. If a RIF comes, you compete for job retention with other people in that area.

Competitive level -- After establishing competitive areas, your agency or organization groups its positions by competitive levels. By the type of work (typist, programmer, personnel specialist) and GS grade, for example. Normally you do not compete for retention with people who have different jobs.

Retention Registers -- By law, federal workers keep, or lose, their jobs during a RIF based on four things: The kind of job and tenure they have; veteran's preference or lack of it; length of federal service; performance.

In a RIF situation, employes are ranked on a "retention register" in three categoris or groups. They are:

Group One: Career employes.

Group Two: Career-conditonal (less than three years service) and career employes serving some kind of probation period.

Group Three: Anyone defined as an indefinite employe, term employe, status-quo employe or employe serving under TAPER (temporary appointments pending establishment of registers).

Each of the three groups is divided into three rating sub-groups. The are:

Ayd, for veterans with compensable service-connected disability of 30 percent or more; A, for veteran, and B, for nonveterans.

Within sub-groups, employes are ranked by service dates, meaning their total amount of civilian federal service and creditable militay service. Anyone with a current "outstanding" performance rating gets an extra four years of service credit.

The RIF is then run on a last-hired-first-fired basis: Employes in the lowest subgroups with the least amount of service are the first fired.

RIFs are tricky. Agencies have considerable competitive areas and functions to be eliminated. That means some people with less service can be saved from a RIF while more senior workers in another area are hit by one. (Some years back the Pentagon ran a one-man RIF to get rid of a whistle-blower).

If you want to know more about RIFs, you personnel office is supposed to have copies of Fed Facts No. 13 on hand. Office of Personnel Management has made them available to agencies. It isn't what you would call fun reading, but it is important and things being the way they are, timely.