Hi Alina, when two or more words are said to be in free variation, that means that they are pronounced differently depending on regions, or gender, or social class. For instance, tomato is pronounced differently in various regions of the world. In North America, it is mostly pronounced "tomayto" (/təˈmātō/) and in Britain, it is usually pronounced "tomahto" ( /təˈmɑːtəʊ/). However, it is pronounced, the listener understands that the speaker refereeing to the same round red vegetable. Therefore, even though the pronunciation differs, depending on the factors, the meaning is the same.