This book investigates semi-modal NEED TO and its semantic variation in Present-day British English. This topic is particularly relevant today, since the use of semi-modals, such as NEED TO, has increased in the field of obligation and necessity, while the frequencies of core modals such as MUST and NEED have decreased. The link of modal change with the process of democratization, and the way the semi-modals offer a less authoritarian way of obliging, present an interesting background for a corpus-based sociolinguistic study. The primary data enables the exploration of NEED TO across variables such as real time, medium, the speaker variables of age, gender and social class, and a number of spoken registers. The results of the five studies in this volume indicate that the functions of NEED TO resemble more and more those of core modals: particularly the directive obligation uses are on the rise.