The use of abbreviations and signs is often a convenience and sometimes a temptation. It is a saving of time and labor which is entirely justifiable under certain conditions, one of which is that all such short cuts should be sufficiently conventional and familiar to be intelligible to any person likely to read the printed matter in which they occur. Scientific and technical signs and abbreviations are part of the nomenclature of the subject to which they belong and must be learned by students of it. General readers are not particularly concerned with them. The use of abbreviations and signs is partly a matter of office style and partly a matter of author's preference. Certain fairly well established rules have, however, emerged from the varieties of usage in vogue. An attempt has been made in the following pages to state these rules clearly and concisely and to illustrate their application. Classified lists of the most common abbreviations and signs have been inserted and will be found useful for reference and practice. Sources of further information on these points will be found under the head of Supplementary Reading.