Key-words are used to define the content of the dissertation and to improve the electronic search of this dissertation. Therefore, they should be representative of its content, clear and specific. They should be selected on the basis of the possible searches by the users of the Digital Library. For example, how would a user be possibly looking for a dissertation concerned with wind energy?
In order to achieve this goal, some common policies are suggested: key-words must be written in plural (e.g. Wind turbines rather than Wind turbine). This rule does not apply when key-words are abstract concepts, for which singular must be used (e.g. Ethics). The table below illustrates the keywords’ use of singular and plural.
| Category | Singular | Plural |
| Material properties | Special case (e.g. Metal conductivity) | General (e.g. Metal properties) |
| Objects, events, objects with special purpose | Vehicles, Lubricants, Neural networks, Controlled loads | |
| Processes, main names, scientific fields, subject areas | Modelling, Lubrication, Earth, Law, Engineering |
Furthermore, unclear key-words or very general and self-evident words (e.g. Design) should be avoided.
In addition, more than one word may be used in the same field, in order to better understand its meaning (e.g., Computational fluid mechanics, Digital imaging, Geographic Information Systems, etc.).
Finally, with regard to the abbreviations that may exist, they should be used only in cases where they are widely established (e.g. GIS for Geographic information systems. Certainly, both GIS and Geographic Information Systems could be used as key-words).
Please, note that key-words should be at least 5 in Greek and 5 in English.
