Nursing is considered a profession and a science (Bousso et al., 2014;Kikuchi, 2014). Nursing knowledge is under continuous development and growth. Therefore, the theory is a hallmark of building an integrated body of knowledge of the nursing discipline (Bhattacharyya et al., 2006) and supports nurses' evidence-based practice (Hoeck & Delmar, 2018). Nursing paradigms and theories have been changing over time. The development of the transformation paradigm at the beginning of the 1970 s changed and developed the panorama of nursing knowledge. This new approach in nursing inspired the development of several new nursing theories, such as Martha Rogers´ Theory of Unitary Human Beings, Jean Watson´s Theory of Human Caring and Madeleine Leininger´s Transcultural Nursing Theory. The middle-range theory by Afaf Meleis, entitled 'Transitions Theory', is well accepted in nursing and has been widely used since then in nursing research, in nursing education and in clinical practice. While taking a master´s degree in the 1960 s, nurse Afaf Meleis realized that patients may experience major transitions, and nurses are in a privileged position to facilitate a health transition. The 'Transitions Theory' book was first published in 2010, which comprises more than 50 articles. Besides that, Meleis had begun publishing the first articles disclosing transitions as a central concept of nursing in the late 1980 s. This theory is founded on the concept of transitions.Understanding what transition means is the first step to understand this theory. The Oxford Dictionary states that the word 'transition' was created in the middle of 16th century, originating from the French or Latin word transire, defined as 'the process or a period of changing from one state or condition to another' (Oxford Dictionary, 2020). According to the theory, transition is a 'complex multidimensional process that both causes and affects changes in life, health, relationships, and environment' (Meleis, 2010, p.359). Transitions can be identified in various ways, such as developmental, health