English and Russian are very different in many important aspects. In particular the grammar systems show significant variations. English has a fairly fixed word order. Meaning is expressed through the addition of words (for example auxiliaries) and movement of words within limited boundaries. Russian, on the other hand, conveys meaning largely through changes in the composition of words (e.g., by inflections or the addition of prefixes and suffixes). Its word order is very fluid. Because of these differences Russians often find learning English a serious challenge.