All 3 terms refer to the same damage inside a tooth although decay and caries are much more accurate descriptions of the disease.
The term cavity is a poor term for describing an area of decay(softness). The reason is that cavity implies there is a hole in a tooth. Even though areas of large decay will usually cause a tooth to collapse and hence form a true cavity, most areas of decay inside a tooth are not easily noticed or visible to a patient and in some cases difficult to be seen by a dentist.
The best lifestyle and dietary choices to keep teeth hard and healthy involve the limiting of sugary foods and acidic beverages ideally to main meal times. The avoidance of frequent sipping and snacking of foods and drinks, other than water, are an important key to making sure “cavities” never form inside a tooth. Staying current with preventive hygienist visits and dental exams are also critical to making sure if a problem forms that it is solved as quickly and conservatively as possible. If you ever have any dental questions about yourself or your family don’t hesitate to let us know.