Roman Numerals
The primary symbols are I 1, V 5, X 10, L 50, C 100, D 500, M 1,000. If a lesser symbol is placed to the right of a greater, its value is added to that of the greater; if it placed to the left, its value is subtracted. Small subtractions from large values are avoided (e.g. 99 is XCIX not IC). Roman numerals may appear in lower case (i, v, x, l, c, d, m), but the practice of printing e.g. viij for viii is now archaic. The sequences IIII, XXXX, and CCCC are occasionally used instead of the usual forms (for example, on old clock faces).
1 I
2 II
3 III
4 IV
5 V
6 VI
7 VII
8 VIII
9 IX
10 X
11 XI
12 XII
13 XIII
14 XIV
15 XV
16 XVI
17 XVII
18 XVIII
19 XIX
20 XX
21 XXI
30 XXX
40 XL
49 XLIX
50 L
60 LX
70 LXX
80 LXXX
90 XC
99 XCIX
100 C
101 CI
144 CXLIV
200 CC
400 CD (or CCCC)
500 D
900 CM (or DCCCC)
1000 M
1900 MCM (or MDCCCC)
1995 MCMXCV
1999 MCMXCIX
2000 MM
Weights, Measures, and Units
Conversion factors are not exact unless so marked.
1. British and American, with Metric Equivalents
Linear Measure
1 inch = 25.4 millimetres exactly
1 foot = 12 inches = 0.3048 metre exactly
1 yard = 3 feet = 0.9144 metre exactly
1 (statute) mile = 1.609 kilometres
= 1,760 yards
1 int. nautical mile = 1.852 kilometres exactly
= 1.150779 miles
Square Measure
1 square inch = 6.45 sq. centimetres
1 square foot = 9.29 sq. decimetres
= 144 sq. in.
1 square yard = 0.836 sq. metre
= 9 sq. ft
1 acre = 4,840 sq. yd = 0.405 hectare
1 square mile = 259 hectares
= 640 acres
Cubic Measure
1 cubic inch = 16.4 cu. centimetres
1 cubic foot = 0.0283 cu. metre
= 1,728 cu. in.
1 cubic yard = 27 cu. ft = 0.765 cu. metre
Capacity Measure
British
1 fluid oz = 0.0284 litre
= 1.8047 cu. in.
1 gill = 5 fluid oz = 0.1421 litre
1 pint = 20 fluid oz = 0.568 litre
= 34.68 cu. in.
1 quart = 2 pints = 1.136 litres
1 gallon = 4 quarts = 4.546 litres
1 peck = 2 gallons = 9.092 litres
1 bushel = 4 pecks = 36.4 litres
American dry
1 pint = 33.60 cu. in. = 0.550 litre
1 quart = 2 pints = 1.101 litres
1 peck = 8 quarts = 8.81 litres
1 bushel = 4 pecks = 35.3 litres
American liquid
1 pint = 16 fluid oz = 0.473 litre
= 28.88 cu. in.
1 quart = 2 pints = 0.946 litre
1 gallon = 4 quarts = 3.785 litres
Avoirdupois Weight
1 grain = 0.065 gram
1 dram = 1.772 grams
1 ounce = 16 drams = 28.35 grams
1 pound = 16 ounces = 0.4536 kilogram (0.45359237 exactly)
= 7,000 grains
1 stone = 14 pounds = 6.35 kilograms
1 hundredweight = 50.80 kilograms
= 112 pounds
1 short ton = 0.907 tonne
= 2,000 pounds
1 (long) ton = 1.016 tonnes
= 20 hundredweight
2. Metric, with British Equivalents
Linear Measure
1 millimetre = 0.039 inch
1 centimetre = 10 mm = 0.394 inch
1 decimetre = 10 cm = 3.94 inches
1 metre = 100 cm = 1.094 yards
1 kilometre = 1,000 m = 0.6214 mile
Square Measure
1 square centimetre = 0.155 sq. inch
1 square metre = 1.196 sq. yards
= 10,000 sq. cm
1 are = 119.6 sq. yards
= 100 square metres
1 hectare = 100 ares = 2.471 acres
1 square kilometre = 0.386 sq. mile
= 100 hectares
Cubic Measure
1 cubic centimetre = 0.061 cu. inch
1 cubic metre = 1.308 cu. yards
= 1,000,000 cu. cm
Capacity Measure
1 millilitre = 0.002 pint (British)
1 centilitre = 10 ml = 0.018 pint
1 decilitre = 10 cl = 0.176 pint
1 litre = 1000 ml = 1.76 pints
1 decalitre = 10 l = 2.20 gallons
1 hectolitre = 100 l = 2.75 bushels
1 kilolitre = 1,000 l = 3.44 quarters
Weight
1 milligram = 0.015 grain
1 centigram = 10 mg = 0.154 grain
1 decigram = 100 mg = 1.543 grains
1 gram = 1000 mg = 15.43 grains
1 decagram = 10 g = 5.64 drams
1 hectogram = 100 g = 3.527 ounces
1 kilogram = 1,000 g = 2.205 pounds
1 tonne (metric ton) = 0.984 (long) ton
= 1,000 kg
3. Temperature
Fahrenheit: water boils (under standard conditions) at 212° and freezes at 32°.
Celsius or Centigrade: water boils at 100° and freezes at 0°.
Kelvin: water boils at 373.15 K and freezes at 273.15 K.
To convert Centigrade into Fahrenheit: multiply by 9, divide by 5, and add 32.
To convert Fahrenheit into Centigrade: subtract 32, multiply by 5, and divide by 9.
To convert Centigrade into Kelvin: add 273.15.
°F °C °C °F
(approx.) (exact.)
-40 -40 -40 -40
-10 -23 -10 -14
0 -18 0 32
10 -12 10 50
20 -7 20 68
30 -1 30 86
40 4 40 104
50 10 50 122
60 16 60 140
70 21 70 158
80 27 80 176
90 32 90 194
100 38 100 212
4. Power Notation
This expresses concisely any power of 10 (any number that is formed by multiplying or dividing ten by itself), and is sometimes used in the dictionary.
102 (ten squared) = 10 × 10 = 100
103 (ten cubed) = 10 × 10 × 10 = 1,000
104 = 10 × 10 × 10 × 10 = 10,000
1010 = 10,000,000,000 (1 followed by ten noughts)
10-2 = 1/102 = 1/100 = 0.01
10-10 = 1/1010 = 1/10,000,000,000
6.2 × 103 = 6,200
4.7 × 10-2 = 0.047
5. The Metric Prefixes
Abbreviations Factors
deca- da 10
hecto- h 102
kilo- k 103
mega- M 106
giga- G 109
tera- T 1012
peta- P 1015
exa- E 1018
deci- d 10-1
centi- c 10-2
milli- m 10-3
micro- m 10-6
nano- n 10-9
pico- p 10-12
femto- f 10-15
atto- a 10-18
6. SI Units
Base units
Physical quantity Name Abbreviation
or symbol
length metre m
mass kilogram kg
time second s
electric current ampere A
temperature kelvin K
amount of substance mole mol
luminous intensity candela cd
Supplementary units
Physical quantity Name Abbreviation
or symbol
plane angle radian rad
solid angle steradian sr
Derived units with special names
Physical quantity Name Abbreviation
or symbol
frequency hertz Hz
energy joule J
force newton N
power watt W
pressure pascal Pa
electric charge coulomb C
electromotive force volt V
electric resistance ohm O
electric conductance siemens S
electric capacitance farad F
magnetic flux weber Wb
inductance henry H
magnetic flux density tesla T
luminous flux lumen lm
illumination lux lx
7. Binary Notation
Only two digits (0 and 1) are used, and the position of each digit in a number indicates a power of two. For example, two is written as 10 (2 + 0), five as 101 (22 + 0 + 1), ten as 1010 (23 + 0 + 2 + 0 = 8 + 2), and one hundred as 1100100 (26 + 25 + 0 + 0 + 22 + 0 + 0 = 64 + 32 + 4).
1 1
10 2
11 3
100 4
101 5
110 6
111 7
1000 8
1001 9
1010 10
1011 11
1100 12
1101 13
1110 14
1111 15
10000 16
10001 17
10010 18
10011 19
10100 20
10101 21
10110 22
10111 23
11000 24
11001 25
11010 26
11011 27
11100 28
11101 29
11110 30
11111 31
100000 32
The Chemical Elements
(in order of atomic number)
hydrogen H 1
helium He 2
lithium Li 3
beryllium Be 4
boron B 5
carbon C 6
nitrogen N 7
oxygen O 8
fluorine F 9
neon Ne 10
sodium Na 11
magnesium Mg 12
aluminium Al 13
silicon Si 14
phosphorus P 15
sulphur S 16
chlorine Cl 17
argon Ar 18
potassium K 19
calcium Ca 20
scandium Sc 21
titanium Ti 22
vanadium V 23
chromium Cr 24
manganese Mn 25
iron Fe 26
cobalt Co 27
nickel Ni 28
copper Cu 29
zinc Zn 30
gallium Ga 31
germanium Ge 32
arsenic As 33
selenium Se 34
bromine Br 35
krypton Kr 36
rubidium Rb 37
strontium Sr 38
yttrium Y 39
zirconium Zr 40
niobium Nb 41
molybdenum Mo 42
technetium Tc 43
ruthenium Ru 44
rhodium Rh 45
palladium Pd 46
silver Ag 47
cadmium Cd 48
indium In 49
tin Sn 50
antimony Sb 51
tellurium Te 52
iodine I 53
xenon Xe 54
caesium Cs 55
barium Ba 56
lanthanum La 57
cerium Ce 58
praseodymium Pr 59
neodymium Nd 60
promethium Pm 61
samarium Sm 62
europium Eu 63
gadolinium Gd 64
terbium Tb 65
dysprosium Dy 66
holmium Ho 67
erbium Er 68
thulium Tm 69
ytterbium Yb 70
lutetium Lu 71
hafnium Hf 72
tantalum Ta 73
tungsten W 74
rhenium Re 75
osmium Os 76
iridium Ir 77
platinum Pt 78
gold Au 79
mercury Hg 80
thallium Tl 81
lead Pb 82
bismuth Bi 83
polonium Po 84
astatine At 85
radon Rn 86
francium Fr 87
radium Ra 88
actinium Ac 89
thorium Th 90
protactinium Pa 91
uranium U 92
neptunium Np 93
plutonium Pu 94
americium Am 95
curium Cm 96
berkelium Bk 97
californium Cf 98
einsteinium Es 99
fermium Fm 100
mendelevium Md 101
nobelium No 102
lawrencium Lr 103
All these elements and their symbols are listed alphabetically in the main part of the dictionary.
All the elements heavier than bismuth (no. 83) are radioactive; all those heavier than uranium (no. 92) have only been produced artificially. The names given above for elements up to 103 are in standard use. Names for elements 104 and above are not yet standardized and have been the subject of controversy:
provisional name suggested names
104 unnilquadium kurchatovium, rutherfordium, (dubnium)
105 unnilpentium hahnium, nielsbohrium, (joliotium)
106 unnilhexium seaborgium, (rutherfordium)
107 unnilseptium (bohrium)
108 unniloctium (hahnium)
109 ? (meitnerium)
The IUPAC provisional names are based on the atomic number and are formed from the numerical roots nil = 0, un = 1, bi = 2, etc. The bracketed names are under consideration by IUPAC; the others have been in informal use.
Chemical Notation
The formula for a compound indicates the number of atoms of each element present in each molecule of the compound: e.g. a molecule of water (H2O) contains two atoms of hydrogen and one of oxygen. The formula for an ionic compound indicates the proportions of the constituent elements, e.g. common salt (NaCl) contains equal proportions of sodium and chloride ions. Formulae for more complex compounds may indicate the manner of combination of the atoms in a molecule: e.g. ethanol (ethyl alcohol) may be represented as CH3CH2OH.
PERIODIC TABLE OF CHEMICAL ELEMENTS
IA IIA IIIB IVB VB VIB VIIB - VIII - IB IIB IIIA IVA VA VIA VIIA 0
(H) He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La1 Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac2 Unq Unp Unh Uns Uno
1Lanthanides La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
2Actinides Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Major Divisions of Geological Time
Era Period Epoch Duration
Quaternary Holocene 100,000 bp to present
Pleistocene 2 mya-100,000 bp
Cenozoic Tertiary Pliocene 5-2 mya
Miocene 24-5 mya
Oligocene 38-24 mya
Eocene 55-38 mya
Palaeocene 65-55 mya
Cretaceous 144-65 mya
Mesozoic Jurassic 213-144 mya
Triassic 248-213 mya
Permian 286-248 mya
Carboniferous 360-286 mya
Palaeozoic Devonian 408-360 mya
Silurian 438-408 mya
Ordovician 505-438 mya
Cambrian 590-505 mya
Precambrian 4,600-590 mya
(bp = before present; mya = millions of years ago)
All figures are approximate and based on currently available evidence.
The Beaufort Scale of Wind Speed
Equivalent speed at
10m above ground
Beaufort Knots Kilometres Description of conditions
number per hour
0 <1 <1 Calm - smoke rises vertically; sea like a
mirror.
1 1-3 1-6 Light air - smoke drifts; ripples on sea.
2 4-6 7-12 Light breeze - wind felt on face, leaves rustle, vanes moved by wind; small wavelets on sea.
3 7-10 13-19 Gentle breeze - leaves and small twigs in constant motion, light flags extend; wave crests begin to break.
4 11-16 20-30 Moderate breeze - dust and loose paper raised, small branches move; fairly frequent white horses at sea.
5 17-21 31-39 Fresh breeze - small trees sway, crested waves on inland waters; moderate waves at sea.
6 22-27 40-50 Strong breeze - large branches move, telegraph wires whistle; foaming crests and some spray at sea.
7 28-33 51-62 Near gale - whole trees in motion, inconvenience felt in walking against wind; foam at sea begins to be blown into streaks.
8 34-40 63-74 Gale - twigs broken off trees, walking upright difficult; wave crests break into spindrift.
9 41-47 75-87 Strong gale - chimney pots and slates moved; high waves at sea with rolling crests and dense spray.
10 48-55 88-102 Storm - trees uprooted, considerable structural damage; sea appears white with high overhanging waves and streaks of dense foam.
11 56-63 103-117 Violent storm - very rare on land, causing widespread damage; sea covered in foam patches, with waves high enough to hide medium-sized vessels and with crests blown into froth, visibility affected.
12 >=64 >=118 Hurricane - sea completely white, with driving spray, the air filled with foam and spray, visibility seriously impaired.
The use of the terms ‘gale’ and ‘storm’ is not completely standardized.