There are some technical contents in your project/thesis topic which contextual meaning may not be well understood by the ordinary man. So, you are expected to define these in a way that readers can understand and flow with. Definition of relevant terms is the process of simplifying the meaning of words or terminology that appears difficult to the ordinary man.
That’s all.
Note: Not all research papers requires definition of relevant terms, however, it is advisable to always seek the opinion of your supervisor for guidance.
Depending on your project topic and the level of technicality, you are suppose to sieve out key words from your topic and simplify them so that readers can easily assimilate and relate those words to your area of focus in the research.
e.g., using the topic “AN ASSESSMENT OF USER-DEMAND PREFERENCE FOR RESIDENTIAL PROPERTIES IN NEW HAVEN LAYOUT, ENUGU”
The key words would include; user-demand, users’ preference, demand, residential property, property etc. furthermore, you will simplify the key words by throwing in simple definitions that even non researchers or people outside your field of study can comprehend with little effort.