There are quite different concepts of nouns (podstatné mená) in Slovak and English, and the Pinkerton piece provides some good examples. The concept of countable and uncountable words is very important in English, because the former can be used in the plural (množné číslo) whereas the latter (usually) cannot.

This is not such a crucial difference in Slovak (it's enough having to remember how to inflect the paradigms "dub", "stroj", "hrdina", and so on), so there's no problem saying "dve školenia" (except for somebody from Eastern Slovakia, of course ;-). In English, though, the word "training" is uncountable, so if you want to say "two", then you'd better use the word "course" and say "two training courses". By the way, I thought William Pinkerton set up a private detective agency during the American Civil War - so now they call it "project management".