- An individual, group, structure, or other entity regarded as an elementary structural or functional constituent of a whole. (noun)
- A group regarded as a distinct entity within a larger group. (noun)
- A mechanical part or module. (noun)
- An entire apparatus or the equipment that performs a specific function. (noun)
- A precisely specified quantity in terms of which the magnitudes of other quantities of the same kind can be stated. (noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.