In English today, an apparatus can refer to a piece of equipment, a structure, or a part of a whole, but when it was first borrowed into English in the 1620s, it particularly meant "a collection of tools or equipment". This was taken from Latin apparatus, which held a variety of definitions, including "tools", "preparation", "implementation", and "equipment". The "prepare" meaning is most important as we go back in time, since apparatus came from the verb apparare, which meant "to prepare" and was composed of the prefix ad-, "to", and the root parare, "make ready". Therefore, an apparatus makes something ready, or prepares it. Ad- comes from a Proto-Indo-European root with the same definition, and parare is reconstructed as deriving from PIE per, meaning "produce". Usage of the word apparatus spiked during World War I and has been on the decline since, but Google searches for the term have remained relatively constant over the years.
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