Series /si-rííz/ and serial /si-riel/ - once again, two English words for the one which is used in Slovak. They are very similar, but there is a difference in meaning if you really want to use them appropriately. They both mean a sequence of TV programs with a common theme and possibly the same people appearing in them, but in a serial there is one long main story divided up into episodes, each of which probably ends with a very tense moment called a "cliffhanger" (cliff is "útes" and hang is "vešať sa") which is intended to make us watch the next episode, while a series consists of separate episodes each with an independent story or situation that is resolved at the end of each one.

You can say that the Spanish/Mexicans/Argentinians make unbelievable serials (otherwise known as soap operas, because they were originally simple entertainment vehicles for presenting adverts for washing powders), while the BBC make incredible natural-history documentary series like Walking with Dinosaurs.