In United States full professorship is a path to take right after PhD, while in many European countries the preconditions to start a full academic career are different. The highest academic degree in some European educational systems is called “habilitation”, which is awarded not as a degree, but rather as a professional qualification for University professors.
The countries, where habilitation is an indicator of the highest academic achievements, as well as the possibility to supervise PhD students and younger researchers, are Germany, France, Spain, Czech Republic and others. Depending on specific country requirements it takes from five to ten years to complete the habilitation, which is a post-doctoral academic award. Holders of habilitation qualify as senior academics and high level scholars: this demonstrates the ability to conduct independent research and to fundraise for this type of initiatives. This highest academic award is approved and granted by a joint special commission.
Post-docs pursuing a habilitation award submit a broader thesis than the PhD dissertation to show even more in-depth analysis of research issue. The same, certainly, concerns the academic publications, submitted in the course of habilitation.
Cumulative habilitation is another term used to indicate the research process, during which the person turns from one scientific field to another, e.g. from applied math to pure math. It is more than possible to hold a PhD in chemistry, while get the habilitation in biochemistry.
Habilitation equals to full professorship: a term more typical for US academic system. In Russia, for instance, it is fully equivalent to “doctor nauk” award, that is achieved after PhD studies and demonstrates even higher academic achievements.