When creating a feed if you enter one keyword will it also capture other similar keywords in the feed?

An example on how to, best works with individual keywords or multiple keywords to get the results you are looking for

When creating a feed, if you enter a keyword, e.g. pesticides, will this identify all posts which relate to that topic, e.g. herbicides, fungicides, MRLs, or will it only identify articles that have the exact keyword included in the title or text?

Our research is based on an Ontology that allows us to relate entities and its close variations. 

In this example, if the target feed is wider than "pesticides" alone, the best approach would be select Pesticides as substance in the search 

In this way, you will be searching for pesticides and for all terms related to pesticides as synonyms and as children: you can see the list by clicking on the gray box Substance: Pesticides