Not every digital model is a digital twin: an epidemic of misconception

The growing popularity of emerging technologies—particularly in equipment monitoring and diagnostic applications—has led to the increasing use of appealing and modern-sounding terms such as virtual sensing, artificial intelligence, and, more recently, digital twins. However, this letter aims to raise awareness of the widespread misconceptions surrounding the concept of digital twins, which both specialists and non-specialists often misapply. The key question is: Are all methods labeled by their authors as "digital twins" truly digital twins? This letter presents a brief overview of the terminology and definitions involved to clarify and promote the correct use of the term digital twin—reserving it only for cases where there is a true virtual counterpart that maintains real-time, bidirectional communication with its physical system.