+1 It seems that vacuum is the odd word out when placed in a lineup with (for example) continuum, individuum, menstruum, and residuum. I don't know why the -uum in vacuum came to be pronounced differently from the -uum in the others, but to judge from the pronunciation offered in John Walker's A Critical Pronouncing Dictionary, and Expositor of the English Language (1807), 'twas not always thus.
I noticed Robin Michael, who is on this site, stated she learned to spell the word 'vacuum' as "vacumn". I was also taught the same thing in school around 40 years ago; I always scored the
(In a vacuum, “Am I not?” could only be construed as some sort of philosophical counter-Descartian pondering.) In light of this dependence, the comma is more apt then the semicolon.
If a 'vacuum cleaner cleaner' is a machine for cleaning vacuum cleaners, then the person who cleans the vacuum cleaner cleaner would be a 'vacuum cleaner cleaner cleaner'.
In other words, don't talk about how the vacuum cleaner was made in Germany and incorporates the latest technology; tell the client he'll be able to vacuum the house in half the time and he'll never have to buy a replacement bag.
Considering their primary meanings, vacuum is used more often in a scientific context, in which case it means space completely or partially absent of any matter/air. It is a scientific term, while void can be used non-technically in a more abstract sense, but it can also be used when talking about empty space in a non-scientific way.
This property of a vacuum tube to create the electronic current in vacuum and act as an amplifier is the base of what is called electronics, to distinguish it from the other fields of electrical engineering. Electronics was born with the vacuum tube. From tube to transistor (and semi-conductors in general)