Be warned though that none of these rules are completely reliable. Things which usually come as part of a series or group, or which are not normally identified individually, are usually t-words. Nouns which are unchanged in the plural are almost always t-words and vice versa. Languages are t-words, because of sprog. Countries are t-words, because of land.
Substances are t-words.
Hence additiv, casino, circul re, cv, forum, hotel, job, system, tribunal, trick, universitet. This page maintained by Gordon Smyth , Department of Mathematics , University of Queensland .