- Sloping or joining something at an angle that is not a right angle.
- Neither perpendicular nor parallel to another line or plane.
oblong 长方形的,矩形的；椭圆形的
Having the shape of or resembling a rectangle or ellipse.
obtuse angle 钝角
An angle greater than 90° and less than 180°.
obtuse triangle 钝角三角形
A triangle with one obtuse angle.
octagon 八边形
A polygon with eight sides and eight angles.
octahedron 八面体
A polyhedron with eight faces.
odd 奇数的
- Not divisible by two.
- Changing sign but not absolute value when the sign of the independent variable is changed, as in y = x3.
odd number 奇数
Designating an integer not divisible by two, such as 1, 3, and 5.
odometer 里程表
An instrument that indicates distance traveled by a vehicle.
open sentence 开命题,真伪未定的命题
An expression that contains at least one unknown quantity and becomes true or false when a test value is substituted for the unknown.
operation 运算
A process or action, such as addition, substitution, transposition, or differentiation, performed in a specified sequence and in accordance with specific rules.
operator 运算符
A symbol for expressing a mathematical operation.Such as +, -, ×,÷
order 排序
A condition of logical or comprehensible arrangement among the separate elements of a group.
order of operations 操作顺序
A collection of rules that reflect conventions about which procedures to perform first in order to evaluate a given mathematical expression. For example, in mathematics and most computer languages, multiplication is granted a higher precedence than addition.[1] Thus, the expression 2 + 3 × 4 is interpreted so as to have the value 14, not 20.
ordered pair 有序对
An ordered pair (a, b) is a pair of objects. The order in which the objects appear in the pair is significant: the ordered pair (a, b) is different from the ordered pair (b, a) unless a = b. In contrast, the unordered pair {a, b} equals the unordered pair {b, a}.
ordinal number 序数词
A number indicating position in a series or order. The ordinal numbers are first (1st), second (2nd), third (3rd), and so on.
ordinate 纵坐标
In plane Cartesian coordinates, the y-coordinate of a point: its distance from the x-axis measured parallel to the y-axis.
origin 原点
The point of intersection of coordinate axes, as in the Cartesian coordinate system.
orthocenter 垂心
The point of intersection of the three altitudes of a triangle.
ounce 盎司
A unit of weight in the US Customary System, an avoirdupois unit equal to 437.5 grains (28.35 grams).
outlier 离群值；异常值
An observation that is well outside of the expected range of values in a study or experiment, and which is often discarded from the data set,
oval 椭圆形, 卵形
An egg-shaped or elliptical form or figure.
