## vigesimal Quick reference

### A Dictionary of Weights, Measures, and Units

...[a composite adjective from Greek and Latin for 20] With divisor/multiplier steps of 20, in contrast with the steps of 2 for binary , of 10 for decimal , of 60 for sexagesimal ,...

## body mass index Quick reference

### A Dictionary of Weights, Measures, and Units

...mass index health . The ratio of a person's mass in kilograms to the square of their height in metres. Providing a rough correction for mass relative to height, it is approximately 20 for a ‘trim’ person, 25 for overweight, 30 for...

## twenty-twenty Quick reference

### A Dictionary of Weights, Measures, and Units

...Now a general phrase indicating perfection. medicine . (correctly twenty/twenty ) The representational figure for what is regarded as perfect human vision, the ability to identify an alphanumeric character ⅓ in (8 mm) high at a distance of 20 ft (6.1∼ m). Applied separately to each eye, the latter figure is increased for sub-normal vision proportionally to the increase in size necessary for identification; thus 20 / 30 indicates an eye that can identify at 20 ft what a normal eye can identify at 30 ft, equivalently how much the standard...

## kiloton Quick reference

### A Dictionary of Weights, Measures, and Units

...or metric) tons of the explosive trinitrotoluene (TNT) ≈ 4.2∼ GJ (coincidentally ≈ 1 Gcal). The atomic bombs dropped in 1945 on Japan had the energy of about 20 kilotons. Modern ‘tactical’ atomic weapons, relying primarily on fission, have a power in the range 0.1 to 20 kilotons from less than a kilogram of plutonium; ‘strategic’ weapons may be of several hundred kilotons, using fusion triggered by a small fission bomb. See also megaton...

## basis point Quick reference

### A Dictionary of Weights, Measures, and Units

...point A unit at the level to which a particular figure is routinely expressed, regardless of the position of the decimal point. Thus, if interest rates are normally expressed (as a percentage) to two decimal places, then a rise from 5.41 to 5.61 would be termed a rise of 20 basis points (and had it risen by 19, one should say to 5.60 rather than 5.6). That rise of 20 basis points could also be described as a rise of 0.2 percentage points , this latter expression being independent of the number of decimal places cited. (A rise of 0.2 from 5.41 is a rise of...

## SAE Quick reference

### A Dictionary of Weights, Measures, and Units

...[Society of Automotive Engineers, USA] engineering . A scheme for grading lubricating oils according to their viscosity under varying temperature conditions. Approximate equivalents in centipoises are in Table 45. Table 45 at: 0°F (-17.8°C) 100°F (-37.8°C) 210°F (-98.9°C) SAE 10W 1 950 41 6.0 SAE 20W 6 550 71 8.5 SAE 30 114 11.3 SAE 40 173 14.8 SAE 10W-30 76 12.7 SAE 20W-40 93...

## noise rating number Quick reference

### A Dictionary of Weights, Measures, and Units

...rating number acoustics . Particularly for measuring aircraft and similar noise, the product of noise level in decibels and a factor dependent on frequency (factor = 1 at 1 kHz), the level being measured relative to a minimally perceptive increment of 20 μPa in r.m.s . pressure. Harris C. M. Handbook of Noise Control (New York: McGraw-Hill,...

## mega- Quick reference

### A Dictionary of Weights, Measures, and Units

...[Gk: ‘great’] Symbol M-. Metric The 10 6 multiplier, e.g. 1 megajoule = 1 MJ = 10 6 J; contractable to meg- before a vowel, e.g. 1 megohm = 1 MΩ = 10 6 Ω. informatics . Sometimes 1 048 576 = 2 20 , but see mebi- then kibi-...

## noy Quick reference

### A Dictionary of Weights, Measures, and Units

...[annoyance] acoustics USA 1 noy = the loudness of a random noise in the band 910 to 1 090 Hz at 40 db above the standard listener's threshold of 20 μPa. ( Compare sone .) Higher values correspond to the increase in physical intensity in the same proportion increase in loudness relative to intensity. Kryter K. D. J. Acoust. Soc. Amer. 31, 1415–29...

## phon Quick reference

### A Dictionary of Weights, Measures, and Units

...acoustics . Symbol P. A measure of loudness level, as agreed in 1937 at the first International Acoustical Conference, Nature 140, 370 (1937) the decibels of sound pressure above 20 μPa of a pure tone of 1 000 Hz subjectively judged by a group of listeners as equally loud as the sound being measured. ISO 131:1979 Acoustics – Expression of Physical and Subjective Magnitudes of Sound and Noise in Air (The reference pressure was 316 μPa earlier.) If p and s represent the loudness respectively in phons and sones, then p = 40 + 10 log 2 s...

## sone Quick reference

### A Dictionary of Weights, Measures, and Units

...acoustics . 1 sone = the loudness of a simple tone of 1 kHz at 40 db above the standard listener's threshold of 20 μPa (≈ the hum of a modern refrigerator). ISO 131:1979 Acoustics – Expression of Physical and Subjective Magnitudes of Sound and Noise in Air A sound twice as loud has value 2, etc. Kryter K. D. J. Acoust. Soc. Amer. 31, 1415–29 (1959) If s and p represent the loudness respectively in sones and phons, then s = 2 ( p -40)/10...

## I.Q. Quick reference

### A Dictionary of Weights, Measures, and Units

...[ Intelligence Quotient ] The usual measure of intelligence, now assessed by standardized tests that supposedly measure the innate, untrainable intelligence of an individual in a fully objective way. Originally created to measure the mental ‘age’ of children as a percentage of real age, a value of 100 is thus inherently normal. Values obtained for adults range fairly widely, from about 20 to 200. There is continuing scepticism about IQ tests, and doubts about their objectivity, the innateness of what they measure, and their correlation with meaningful mental...

## fluid ounce Quick reference

### A Dictionary of Weights, Measures, and Units

...ounce volume . Symbol fl oz, also liq oz. Volume of 1 oz avoirdupois of water. BI 1 / 20 BI pt = 1 / 160 BI gallon = 28.413∼ mL – see Table 16(a). US-C (Symbol also liquid ounce, liq oz) Solely for liquids, 1 / 16 US pt = 1 / 128 US gallon = 29.574∼ mL; see Table 16(b). Table 16(a) BI SI US-C liq minim … … … 59.2∼ μL 0.0200∼ oz 60 fluid dram … … 3.55∼ mL 0.120∼ oz 480 8 fl oz … 28.4∼ mL 0.961∼ oz 20 pint 568.∼ mL 19.2∼ oz See gallon for upward extension. Table 16(b) US-C liq SI minim … … … 61.6∼ μL 60 fluid dram … … 3.70∼ mL 480 8 fl oz, liq...

## poise Quick reference

### A Dictionary of Weights, Measures, and Units

...] dynamic viscosity . Symbol P. Metric-c.g.s. Identically dyne⋅second per square centimetre (dyn⋅s⋅cm -2 ) = 10 -1 N⋅s⋅m -2 = 10 -1 Pa⋅s(= cm -1 ⋅g⋅s -1 in c.g.s. base terms). Hence • P⋅(g⋅cm -3 ) -1 = stokes for kinematic viscosity. The poise is a large unit for most purposes, water at 20°C having a viscosity of 10.020∼ mP and most free-flowing liquids typically being similar; gases are around 1 μP. There is no equivalent special term in the...

## preferred numbers Quick reference

### A Dictionary of Weights, Measures, and Units

...numbers , preferred values engineering . A (near-) geometric series of numbers, providing a pre-defined count of essentially consistent multiplicative steps to a set objective, typically an overall multiplication by 10. The formalization of this simple mathematical process is attributed to a Capt. Renard in France, who applied it to the mooring ropes for balloons in the 19th century, reportedly reducing the variety stocked from over 400 to under 20. (Modern usage is most common for electronic components.) A series of preferred numbers could be truly...

## twenty-foot equivalent unit Quick reference

### A Dictionary of Weights, Measures, and Units

...The standard element of the containerized shipping scheme, being a box 8 ft by 8 ft in cross-section times 20 ft long, hence of volume 1 280 ft 3 (36.245 6∼m 3 , 32 shipping ton). Such a container may be a simple steel box, a steel frame holding a round tank, or any other entity meeting the standard dimensions for size, strength, position of fasteners, etc. Multiples and a 10 ft half unit (actually the pioneer size) exist, reckoned proportionally to the twenty-foot unit for relevant statistics. (A height other than 8 ft is also...

## windchill (factor) Quick reference

### A Dictionary of Weights, Measures, and Units

...(factor) Canada A composite of temperature and wind speed, constructed to reflect the greater freezing effect, particularly on hairless human skin and flesh, of low temperatures when accompanied by significant wind. The initial form consisted merely of subtracting the Fahrenheit temperature from the wind speed measured in miles per hour, e.g. a wind of 20 m.p.h. and a temperature of -30°F gave a windchill of 50, equatable with -50°F in calm conditions. The real effect is far from linearly additive in such a simple (and convenient) manner. Careful study...

## sexagesimal Quick reference

### A Dictionary of Weights, Measures, and Units

...[Lat: ‘sixtieth’] With divisor/multiplier steps of 60, in contrast with the steps of 10 for decimal , of 12 for duodecimal , of 20 for vigesimal , etc. The sexagesimal approach was dominant in Ancient Mesopotamia, and survives today on the clock and in the degrees for measurement of plane angles. Babylonian numerals had a composite two-part structure, the first counting 0 to 4 dozens, the second part 0 to 11 units, the composite 4, 11 meaning 59, i.e. 1 short of...

## decimal Quick reference

### A Dictionary of Weights, Measures, and Units

...With divisor/multiplier steps of 10 between units, in contrast with the steps of 2 and its powers for binary and its compounds, of 12 for duodecimal , of 16 for hexadecimal , of 20 for vigesimal , and of 60 for sexagesimal , etc. The original metric system of the 1790s made decimal scaling usual in Europe, though it had then been usual in China for a thousand years. The SI system , although nominally decimal through its metric heritage, is largely millesimal , i.e. in steps of 1 000. Steps of 100 are centesimal...

## pennysize Quick reference

### A Dictionary of Weights, Measures, and Units

...USA A scheme for expressing the size of nails, from finishing nails to spikes, expressed as a number followed by the symbol d for penny in the English tradition. The lowest value is 2d, representing a nail of length 1 in; to value 8d the length increments by ¼ in, making the latter value correspond to 2½ in. The only further values are 10d for a length of 3 in, 12d for 3¼ in, 16d for 3½ in and 20d for 4 in. The scheme appears to reflect the cost of one hundred nails of the size, at some past point of time, with ‘penny’ relating to the vernacular name...