The word "RA" can have multiple meanings depending on its context. Here are some possible definitions:
1) Radio Amateurs - a term used to refer to hobbyists who operate radio stations in their homes or other locations, often for recreational purposes and community service.
2) Radiologist Assistant- an allied health professional who works under the supervision of a radiologist to perform diagnostic imaging procedures.
3) Rheumatoid Arthritis - a chronic autoimmune disorder that primarily affects joints, causing pain, swelling and stiffness. It is caused by an overactive immune system attacking the body's own tissues.