玄数

handspan     一掌之宽
A unit of length based on the width of an expanded hand, usually taken as nine inches.

hectare (ha)     公顷
A unit of surface, or land, measure equal to 100 ares, or 10,000 square meters: equivalent to 2.471 acres.

heft     重量

• US weight
• To assess the weight of (something) by lifting.

height     高度

• The distance between the lowest and highest points of a person standing upright.
• The distance upward from a given level to a fixed point.

hemisphere     半球

• One half of a sphere.
• One half of the Earth, especially a half north or south of the equator or west or east of the prime meridian: Eastern Hemisphere, Western Hemisphere, Northern Hemisphere, Southern Hemisphere.

hendecagon     十一边形
A polygon with eleven sides and eleven angles.

heptagon     七边形
A polygon with seven sides and seven angles.

hexadecimal     十六进制
A number system having a base 16; the symbols for the numbers 0–9 are the same as those used in the decimal system, and the numbers 10–15 are usually represented by the letters A–F. The system is used as a convenient way of representing the internal binary code of a computer.

1201 = 4×16² + 11×16¹ + 16⁰ —— 4B1

hexagon     六边形
A polygon with six sides and six angles. wikipedia-Hexagon

hexahedron     六面体
Cube, a polyhedron with six faces. wikipedia-Cube

highest common factor     最大公因数
Greatest common divisor: the largest number or quantity that is a factor of each member of a group of numbers or quantities.

Hindu-Arabic Number System     印度 – 阿拉伯数字系统

histogram     直方图
A diagram which uses rectangles (= bars) of different heights (and sometimes different widths) to show different amounts, and the area of each bar represents the frequency of that value, so that they can be compared.

horizontal     水平的；水平线
At right angles to the vertical; parallel to level ground.

hour     小时

• 60 minutes; one of the 24 parts that a day is divided into.
• Any specific one of these 24 periods, usually reckoned in two series of 12, one series from midnight to noon and the second from noon to midnight, but sometimes reckoned in one series of 24, from midnight to midnight:
  He slept for the hour between 2 and 3 a.m.

hour hand     时针
The small hand on a clock or watch that points to the hour.

hundredth     百分之一; 第一百

• One of 100 equal parts: 1/100.
• The ordinal number matching the number 100 in a series.

hyperbola     双曲线
A conic section formed by a point that moves in a plane so that the difference in its distance from two fixed points in the plane remains constant.
| M₁F₁ | – | M₁F₂ |  =  | M₂F₁ | – | M₂F₂ |  =  | M₃F₁ | – | M₃F₂ | =  …… = Constant.

hypotenuse     斜边，弦
The side of a right triangle opposite the right angle.

hypothesis     假设
An idea or explanation of sth that is based on a few known facts but that has not yet been proved to be true or correct.