ATM
PubMed uses automatic term mapping to make more complicated, complex, and thorough searches from my simple searches (find this by selecting "Advanced" below the search bar). If you select the > under details to see how PubMed translated the search.
Here are the results from the search "what causes gout"
Notice that the number of results are very different for the searches "how are senior citizens affected by isolation and covid 19" and "senior citizen isolation covid 19".
And here are the results from the search "cause gout". Note that they retrieve the same number of results. That does not always happen depending on the keywords you use.
