This book presents a study of language - and how a certain type of word can be used as a tool of control. The terms that are used in relation to certain social and political issues can affect perception, cognition, emotion and behaviour. Certain terms are of the form that can obscure issues, confuse and manipulate people - hence facilitating social and political control. In particular this book examines the meaning of the term 'multiculturalism' (and the related terms 'racism' and 'equality'). This examination illustrates much about a certain type of word, including the consequences of using such a word. These terms are nebulous-power-words - of which 'multiculturalism' is shown to be one example (and 'racism' and 'equality' are others). Two perspectives on meaning are taken in this paper: the rational and the social representation perspectives. From a rational perspective, the definition of a term is its meaning. For such a definition to be adequate it must possess certain characteristics, (e.g. high referentiality). It is shown that 'multiculturalism' is rationally inadequate, but its irrationalities can be explained from a social representation perspective - an approach that demonstrates, amongst other things, how an irrational term can be used in communication and what meaning it holds to people. As a term that is inadequate from a rational perspective, such a term should not be used in rational discourse - the fact that it is renders such discourse inadequate. As a specific type of irrational term, nebulous-power-words are emotional and powerful - and the power of such terms is contingent upon their lack of rationality and the fact that people do not realise their true nature. Without these characteristics the emotional content could not exert the power that it does. Terms of this kind can exert control by, amongst other things, obscuring truth, inhibiting rationality, confusing people and distorting perception - and hence, inter alia, the emotions and social forces associated with such terms can act to manipulate people. It is the very nature of these terms that enables them to operate as powerful tools of control. In the context of 'multiculturalism' such control has been exerted in Britain (and elsewhere) in relation to immigration policies and immigration-related phenomena.