The word 大势所趋 is formed by combining 大 (big) and 势 (trend) into 大势, meaning "general trend", which is then connected to 所 (a particle indicating what is acted upon) and 趋 (to tend towards) into 所趋, meaning "where things are heading", resulting in a phrase that literally expresses "the general trend is moving towards" to denote an inevitable direction.