The development of Language Engineering and Information Retrieval applications for Arabic require availability of sizeable, reliable corpora of modern Arabic text. These are not routinely available. This paper describes how we constructed an 18.5 million word corpus from Al-Hayat newspaper text, with articles tagged as belonging to one of 7 domains. We outline the profile of the data and how we assessed its representativeness. The literature suggests that the statistical profile of Arabic text is significantly different from that of English in ways that might affect the applicability of standard techniques. The corpus allowed us to verify a collection of experiments which had, so far, only been conducted on small, manually collected datasets. We draw some comparisons with English and conclude that there is evidence that Arabic data is much sparser than English for the same data size.