First, for the original technical meaning, the meaning I knew and loved before the days of digital:<2010 It was a much different place then even during the Bush Sr. administration,’ says Joe Hagin, Bush 43’s deputy chief of staff, who also worked for Reagan and Bush 41. ‘There was much less time [under the second Bush] to catch your breath during the day.’ He recalls the constant juggling of issues—from the wars to Katrina—often all at the same time. ‘There’s only so much bandwidth in the organization,’ he says.”—Newsweek, 22 November, page 30>
1) BANDWIDTH noun [[1920s]]: The numerical difference between the upper and lower frequencies of a band of electromagnetic radiation, especially an assigned range of radio frequencies [[Note that this bandwidth refers to analog and not digital signals and probably should be called ‘analog bandwidth’]]. (American Heritage Dictionary)
For an electric circuit designed to operate between 1000 HZ and 7000 Hz, the bandwidth would be the difference, which is 6000 Hz. Outside of this range the circuit may not operate properly or may even have a frequency of zero in the case of a frequency filter. As an example, a television station may have been assigned a bandwidth of 6 MHz between two particular frequencies.
With advent of computers and digital signal processing, bandwidth took on a second technical meaning:
2) BANDWIDTH: noun [[1990s]]: The quantity of data that can be passed along a communications channel in a given period of time. [[This is a rate of data transfer (information carrying capacity, data transmission capacity) measured in bits per second (bps)]] (American Heritage Dictionary) [[Note: There does exist a relationship between this bandwidth and the above bandwidth (Nyquist–Shannon Theorem)]]
Note: Dates for the bandwidth definitions provided above and below come from the earliest quotes I was able to find.
The New Hacker’s Dictionary by E.S. Raymond
BANDWIDTH noun: Used by hackers . . . as the volume of information per unit time that a computer, person or transmission medium can handle. Those are amazing graphics, but I missed some of the detail—not enough bandwidth I guess.
[[Note: Bandwidth can range from high to low.]]
LOW BANDWIDTH [from communications theory]: Used to indicate a talk that, although not content-free, was not terribly informative. That was a low bandwidth talk, but what can you expect for an audience of suits! [[Also, A person with low bandwidth is ‘slow on the uptake’; unable to multitask]]
So, when you hear of computer folks wanting more bandwidth, what they want is more data transmission capacity. The more bandwidth, the more data can be transferred in a given period of time – ‘the faster the connection.’
In popular (nontechnical) usage BANDWIDTH has taken on several meanings:
BANDWIDTH noun (idiom/slang) [1990s]: capacity, range, resources, content, range of knowledge, diversity of expertise, intelligence, mental capacity, aptitude, time, multitasking ability, mental or physical processing capacity. (And it is not always clear which one is meant). [Since the non-technical ‘bandwidth’ hasn’t made it into any of the dictionaries I checked, these definitions were inferred from sifting through quotes]
The following quotes are from archived sources:
_______________________<1992 “To Gates, who has gone through a steady stream of No. 2 executives, Hallman didn’t have enough ‘bandwidth’– a favorite Gates word for breadth of intelligence – to keep up with the company and its chairman.”—Hutchinson News (Kansas, 29 March, page 113>
<1996 “In addition to enjoying an intimate understanding of the business [[stock analysis]] or, in the local slang, ‘sufficient intellectual bandwidth,’ these firms also have deep roots in the community.”—Insight on the News, 22 April>
<1997 “Part of what makes him so enigmatic is the nature of his intellect. Wander the Microsoft grounds, press the Bill button in conversation and hear it described in computer terms: he has ‘incredible processing power’ and ‘unlimited bandwidth,’ an agility at ‘parallel processing’ and ‘multitasking.’ ibid. Microsoft has long hired based on I.Q. and ‘intellectual bandwidth.’”—Time Magazine,13 January>
<1998 “‘Instead of asking if we have time to do something or aptitude to handle a project, (clients) want to know if we have the ‘bandwidth,’ said Chris Lind, an executive at a public relations agency . . .”—Buffalo News (New York), 28 February>
<1999 “Because the bandwidth of opportunity is limitless for workers with the right skills . . . “—Twin Falls Times News (Idaho), 6 September, page 11>
<2001 “BANDWIDTH: Time, in the context of your modem and your internet service provider's information-carrying capacity and speed. Can also be applied to humans, viz, ‘I'd love to help you with that inordinately time-consuming project, but I simply don't have the bandwidth.’”—The Independent (London), 3 November>
<2008 “‘Barack Obama not only had the good judgment to oppose the war in Iraq but, as he told us earlier this year, 'I want to end the mind-set that got us into war.' So it is troubling that a man of such good judgment has asked Robert Gates to stay on as secretary of defense - and assembled a national security team of such narrow bandwidth,’ Miss vanden Heuvel said.”—Washington Times, 2 December>
<2010 “Indeed, in an era in which music occupies an increasingly thin, crowded cultural bandwidth, being a ‘multi-platform operation is essential. ‘Even when we were working on tracks, she’d be putting pictures together and getting images off Google . . . she was always thinking about the whole package.’”—Spin, Vol. 26, No. 7, August, page 68>
Ken G – December 12, 2010