laravel unique validation with both singular and plural words

I want laravel to check for uniqueness of words in the database table for both singular and plural of a word. That is only one instance of either singular or plural word should exist. For example If user enters chocolate and if database has chocolates or chocolate then the validation should fail. The reason for this is that the data is stored in database as a plural of word.So when user enters singular word then validation passes but it actually gets stores as plural. Here is my code.

 public function update(Request $request, Category $category)
        {
            if (!$request->hasAny('category_status')){
                $this->validate($request, [
                    'category_name' => [
                    'required','max:255',
    
                    Rule::unique('categories', 'category_name')->where(function ($query) {
                    $categoryName = Str::plural(request()->category_name);
                    return $query->where('category_name', $categoryName);
                })->ignore($category)
    
                ],
                ]);
            }
    
       
    
         $category->update($request->all());
            return response()->json(['response'=>__('message.update',['name'=>'category'])]);
        }

The above code only works for exact unique and ignore current model instance. For example if user enters chocolate and database has chocolate than it fails but if it has chocolates only than it passes. I want it to fail for both singular and plural. Thank you