This thesis is concerned with the linguistic description of hashtags and the definition of common as well as platform- and gender-specific usage-patterns. As the Internet expands and develops, the channels and modes of online communication are constantly changing, shaping what is often described as the Web 2.0; a conglomerate of evolved Internet applications, which has come to be defined by its emphasis on communication. In this ‘age of social media, hashtags constitute a relatively recent feature of computer-mediated communication, and have, hitherto, not received equally broad academic attention as many other salient aspects of CMC. Hence, this thesis provides an extensive theoretical analysis of hashtags, including their linguistic properties and various functionalities, such as tagging and commenting. In further consequence, the thus established categories are examined according to usage-frequency and patterns by means of 155 self-administered questionnaires, which provides valuable insights into gender- and platform-specific hashtag use, as well as age-related sample deviations. The detailed presentation and discussion of the survey serves to illustrate gender-related differences in user-intention as well as the influence of social media platforms on general hashtag-usage, ultimately providing a thorough sociolinguistic analysis of this emerging CMC feature.