Recent developments in the control systems of aeroplanes have been such as to underline the need for new terms, and the need to remove any ambiguity relating to terms already in existence. The question has also been raised by the British Standards Institute in relation to the revision of the Glossary of Aeronautical Terms. The present paper examines the problem in the light of possible future developments, lists proposed terms with their definitions, and gives an outline of the underlying arguments. It is written in the spirit that in the field of systems of units, notation, and nomenclature “survival of the fittest” will always apply. The details of the nomenclature are not considered all-important, but we have tried to select the right concepts, to classify sensibly, and to produce accurate and general definitions. We expect many useful and amusing comments on nomenclature, but the other aspects are the fundamental ones, and we hope there will be some constructive criticism.