Key concepts are main ideas.Research is iterative, e.g. after searching for sources, you may need to redefine your research topic and change the key concepts.
Some databases use NOT, some use AND NOT to mean the same thing. NOT/AND NOT is tricky to use as you may unwittingly exclude articles that are relevant to your research. For example, an article may contain only a passing mention of term B. Use with caution, only if you’re sure of what you’re doing.
Truncation at the end of a stem/alternative spellings (American and British)/singular or plural forms of a word.Some databases use * and others use ? --> Check the FAQ/help/guides.
If the catalogue or database does not use these exact phrases, you may not find anything!A lot of trial and error involved when looking for synonyms. Keep refining your search and trying different methods.
The databases each have their own strengths and limitations. It’s best to use a few instead of just one!