Conditional rewrite on views according to singular / plural
Drupal views provides a singular/plural option, if the field value is an integer type. In your case, if its not available in Field settings try using views_php contrib module. 

This module will allow you to add a field in views with php code that will executed on the fly. You can get existing values of row data inside php from $data variable. Now you can get your output based on the singular/plural in php.

But it is suggested to check the field settings properly if same option is available.