Pattern Design: An Introduction to the Study of Formal Ornament
“The term ‘pattern’ necessarily implies a design composed of one or more devices, multiplied and arranged in orderly sequence. A single device, however complicated or complete in itself it may be, is not a pattern, but a unit with which the designer, working according to some definite plan of action, may compose a pattern. A cross or a circle, a leaf or a bird--or an elaborate combination of several such things, if the result is a self-contained figure--may become the unit-device in a pattern, if it is repeated regularly over a surface. Moreover, a simple line, straight, waved, or abruptly bent, may be in the same way a device unit used as a constituent part of a striped pattern,”
-Pattern Design: An Introduction to the Study of Formal Ornament by Archibald H. Christie