A frame with small balls which slide along wires. It is used as a tool or toy for counting.
In plane Cartesian coordinates, the x-coordinate of a point: its position from the origin (y axis) measured parallel to the x-axis.
absolute value 绝对值
The absolute value of a real or complex number is the distance from that number to the origin. For any real number x the absolute value or modulus of x is denoted by |x|.
Exactly equal to 1⁄640 of a square mile, about 4,046 m2.
acute angle 锐角
The angle is smaller than a right angle (less than 90°)
acute triangle 锐角三角形
A triangle with all interior angles measuring less than 90°
Put numbers or amounts together to get a total.
An addend number which is involved in addition. Numbersbeing added are considered to be the addends.
The process of adding two or more numbers together to find their total.
additive identity 加法恒等元,加法单位元
When added to any element x in the set, yields x. Usually the sum of the number x and 0 yields the same number.
additive inverse 加性逆元
The opposite of a number. For example, the additive inverse of 12 is -12.
adjacent angles 邻角, 同旁内角
Two angles are adjacent when they have a common side and acommon vertex (corner point), and don’t overlap.
A type of mathematics in which letters and symbols are used to represent quantities. Such as: x + 5 = 13, x2 – y2 = 4.
A set of rules that must be followed when solving a particular problem.
alternate exterior angles 外错角
Created where a transversal crosses two lines. Each pair of these angles are outside the parallel lines, and on opposite sides of the transversal.
alternate interior angles 内错角
Created where a transversal crosses two lines. Each pair of these angles are inside the parallel lines, and on opposite sides of the transversal.
The height above sea level.
A quantity of sth.
analog clock / analog Watch 针式台钟
The space between two lines or two rays.
angle bisector 角平分线
Divides the angle into two angles with equal measures.
Happening or done once every year.
annual percentage rate (APR) 年百分率
Interest rate for a whole year.
The region lying between two concentric circles. The area of the annulus formed by two circles of radius a and b (with a > b) is π(a2 – b2).
In the opposite direction to the movement of the hands of a clock.
Given a circle, the apothem is the perpendicular distance from the midpoint of a chord to the circle’s center.
An estimate of a number or an amount that is almost correct, but not exact.
Part of a circle or a curved line. Or a curved shape.
arc length 弧长
The length along a curve.
The amount of space covered by a flat surface or piece of land, described as a measurement.
The most common usage refers to the argument of a function. An argument of a function f(x1, x2, … xn) is one of the n parameters on which the function’s value depends.
The type of mathematics that deals with numerical computation such as the adding, multiplying.
arithmetic sequence / arithmetic series 等差数列
A sequence of numbers such that the difference between the consecutive terms is constant. For instance, the sequence 5, 7, 9, 11, 13, 15 … is an arithmetic progression with common difference of 2.
arm of an angle 角的临边
In general, an arrangement of objects is simply a grouping of them. The number of “arrangements” of n items is given either by a combination (order is ignored) or permutation (order is significant).
A way of organizing and storing related data in a computer memory, such as [1, 2, 5, 10], [ [1,2,3], [10, 20, 30] ]
ascending order 升序
Numbers are arranged from the smallest to the largest number. E.g. 5, 9, 13, 17 and 21 are arranged in ascending order.
associative law 结合律
Giving the same result no matter what order the parts of a calculation are done, for example
(a + b) + c = a + (b + c)
(a × b) × c = a × (b × c)
To think or accept that sth is true but without having proof of it.
A line or curve that approaches a given curve arbitrarily closely, as illustrated in the above diagram.
A quality or feature of sb / sth.
Calculated by adding several amounts together, finding a total, and dividing the total by the number of amounts.
axis 轴 （复数 axes）
A line that divides a shape into two equal parts or an imaginary line through the centre of an object, around which the object rotate.
axis of symmetry 对称轴