preface
Introduction: Before learning units and symbols

Part 1: Seven Worlds Centered on the SI Unit System

CHAPTER 1 Units and Symbols of Time
second [s] minute [min] hour [h] day [d] month [m] year [y]

CHAPTER 2 Units and symbols for length, area, and volume
meter [m] yard [yd] foot [ft] inch [in] square meter [㎡] are [a] hectare [ha] acre [ac] cubic meter [㎥] gallon [gal]

CHAPTER 3 Units and Symbols of Weight
kilogram [㎏] pound [lb] ounce [oz] carat [ct]

CHAPTER 4 Units and Symbols of Electricity, Magnetism, and Electromagnetic Waves
Ampere [A] Volt [V] Watt [W] Electrical resistance [Ω] Inductance [H] Impedance [Ω] Coulomb [C] Faraday constant [F] Farad [F] Weber [Wb] Tesla [T]

CHAPTER 5 Units and Symbols of Temperature
Absolute temperature Kelvin [K] Celsius temperature [℃] Fahrenheit temperature [℉] Melting point [mp] Boiling point [bp] Molal depression constant [Kf]

CHAPTER 6 Units and Symbols of Matter
mole [mol] Avogadro's number [NA] Dalton [Da]

CHAPTER 7 Units and Symbols of Light, Sound, and Color
Candela [cd] Nitrate [nt] Stilb [sb] Lumen [lm] Lux [lx] Decibel [dB] Hertz [Hz] Color Saturation Brightness CIE Color System

Part 2: Units and Symbols of a Special World

CHAPTER 8 Units and Symbols for Understanding Nature
Humidity [%] Pressure [atm] Intensity Magnitude [M] Fujita Scale [F] Reaction Rate [v] Half-life [t1/2]

CHAPTER 9 Units and Symbols in the Quantum World
Atomic mass [Ar(E)] Molecular mass [Mw] Planck constant [h] Planck length [ℓP] Planck time [tP] Bohr radius [a0]

CHAPTER 10 Units and Symbols in the Periodic Table
Element symbol [H, He, Li, Be…] Electron [e] Nucleus [N] Proton [p] Atomic number [Z] Electron shell [K, L, M, N…] Electron orbital [s, p, d, f]

CHAPTER 11 Units and Symbols that Indicate Chemical Properties
Bond lines [―,〓, ≡] Arrow symbols of reaction formulas [→, ↔] Excess/deficiency symbols [δ+] Hydrogen ion index [pH] Acid dissociation index [pKa] Base dissociation index [pKb] Ionization degree [α] Optical rotation [α] Concentration [%] Density [ρ] Hardness Refractive index [n] Transparency Transparency Osmotic pressure [Π] Lethal dose [LD] Effective dose [ED]

CHAPTER 12 Units and Symbols for Strengthening Engineering
Linear velocity [v] Angular velocity [rad/s] Acceleration [a] Tangential acceleration [at] Newton [N] Pascal [Pa] Joule [J] Watt [W] Becquerel [Bq] Gray [Gy]

CHAPTER 13 Units and Symbols for Understanding the Universe
Elementary particle [u, d…] Class [m] Absolute magnitude [M] Parallax [rad] Astronomical unit [AU] Light-year [LY] Parsec [pc] Redshift [z] Solar mass [M⊙]

Appendix Units and Symbols at a Glance 277
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Mastering units and symbols makes science easy and fun!
Master the fundamentals of science! Use them in real life, too!

This book explains units in various fields such as mathematics, physics, chemistry, engineering, and astronomy in an easy-to-understand manner, starting from the fundamental principles and going step by step.
It is not just about mechanically defining the unit itself.
Let's look at the background of how units came into existence and learn about the principles that support scientific phenomena.
It also explains how it is applied academically and how we use it as an indicator in real life.
Information about units and symbols like this can clarify things we vaguely knew, and sometimes even accurately point out errors we took for granted.
Because there are many concepts established over a long period of time, the history of science, stories of scientists, and various general knowledge are also included.

Not many people know the definition of 1 meter.
Interestingly, the basic unit of length, the meter, is determined by the speed of light.
One meter is the distance that light travels in a vacuum in 1/299,792,458 of a second.
There have been several histories leading up to this definition.
We can see the efforts of researchers who constantly corrected errors and tried to establish accurate and universal units.
The unit of volume widely used in English-speaking countries, 'gallon', is a word meaning bucket.
The definition of a gallon varies depending on its use, and since the size of the bucket used to measure different items, such as wine gallons, ale gallons, and oil gallons, is bound to be different for each.
Additionally, the British and American gallons are different, and our country uses the American gallon.
The 'pint', which became famous as a packaging unit for ice cream shops, is also a unit derived from the gallon, meaning one-eighth of a gallon.

The quantum world of calculating atomic and molecular weights, the various chemical formulas and the periodic table filled with complex symbols and letters, are not difficult if you understand the principles.
Not many readers will have looked at this field from a unit-by-unit perspective.
If you look at the core units, symbols, and the principles of how they are used, even complex equations will look different.
If you have a firm grasp of units and symbols, you can see great results not only in physics and chemistry, but also in engineering.
Engineering units and indicators are also extensive, including linear velocity, angular velocity, various accelerations, as well as units of force, energy, pressure, and radiation.
Although it may seem complicated and difficult, it is an engineering unit that can be used and applied repeatedly once you understand it.
This book compares these various units and explains them in an easy-to-understand manner, so you can thoroughly understand the related concepts while reading them in order.

Units are also useful in real life.
For example, 'humidity', expressed as % or g/cm3, has a great influence on the occurrence of fires and the spread of colds.
Even when predicting whether laundry will dry well, you can check the humidity.
We've all heard of lethal dose (LD) and effective dose (ED), but few people know their exact meanings. LD refers to the potency of a poison, and ED indicates the effectiveness of a drug. In fact, the more commonly used terms are half-lethal dose (LD50) and half-effective dose (ED50).
The half-lethal dose, which causes death in 50% of the sample, and the half-effective dose, which causes the drug to be effective in 50% of the sample, can effectively find the drug's effects and side effects.

A stepping stone book that lays the foundation for science

"Dictionary of Units and Symbols: An Easy Guide to the Fundamentals of Science and Engineering" is a basic science book that uses a dictionary-style structure while providing detailed and friendly explanations and examples of relevant concepts.
It is a good book for even the so-called 'science idiots' who are afraid of science to try, as it contains a wealth of reading material and illustrations on related knowledge.
In particular, it was reviewed by current teachers to verify the units officially used in our country and to reflect the terms and concepts used in middle and high school curriculum.
Choi Won-seok, the teacher in charge of the review, is a middle school science teacher and an author who actively works to popularize science.
"A Dictionary of Units and Symbols: A Simple Guide to the Fundamentals of Science and Engineering" is a stepping stone that lays a solid foundation before entering the diverse world of science, and it's also a guidebook you can always keep by your side and consult whenever you're stuck with complex symbols.