We have an Azure Cognitive Search index that we use for full text searches.
Currently, when the user searches for a plural word (e.g. Buildings), the singular forms are also being matched (building).
We want to restrict this behaviour so that only the plural matches are returned.
I've read through the odata documentation but cannot find any reference to how we could accomplish this either through parameters in the search.ismatch in the filter or in the index config.
Plural and singular forms are likely both matching because the field is configured with the default language analyzer, which performs stemming of terms. If you're looking for an exact match, you can use the 'eq' operator in a filter. If you want a case-insensitive (but otherwise exact) match, you can try normalizers (note that this feature is in preview at the time of this writing.)
If you need matching behaviour that is somewhat more sophisticated than a case-insensitive match, you should look into custom analyzers. They allow you to customize the behaviour of tokenization, as well as selectively use (or not use) stemming and other lexical analysis techniques.