What complex tool can be used to convert the type "automobiles" => "car"?

Question

C++ / C#

The input is strings with search preferences, for example, "cats", "cars". You need to get something like "cat", "car" (maybe leave "automobile" as well). In a simple language, you just need to "bring" the words to their "initial" and as "popular" form as possible for further use in the recognition api of various services (since the recognized words there are in the singular and in the most commonly used variants).
For example:

Answer 1

first arrange the wording,
but the problem in general is simply not solved
in the particular - maybe a stemmer will be enough for you

Answer 2

Solved a similar problem.
In my particular case, a dictionary of synonyms turned out to be enough.
Plus morphology, of course.