sad number 
unhappy number, a number that is not happy 
sample 
term in statistics when a portion of the population is tested, and that proportion is said to be representative of the whole population 
sample space 
a list of all the possible outcomes in probability 
satisfy 
a solution is said to satisfy an equation if it produces a true statement. For example, x = 3 satisfies the equation x + 1 = 4 
scalar 
a unit which has size but no direction 
scale 
the marks on a graph or measuring instrument. For example, most rulers have a scale of 1cm or 1mm, sometimes both 
scale 
a scale on a map tells us what ratio is used to compare distances on a map to distances in the real world. For example, a scale of 1:100 tells us for every 1cm on the map, there is 100cm, or 1m in real life 
scalene triangle 
triangle with no equal sides and no equal angles 
scatter diagram 
a diagram in statistics to compare two variables by placing dots to see if a relationship between those variables can be established 
scientific notation 
also known as standard notation. A system to write any number, no matter how large or small so that they are easy to write and compare. Scientific notation is of the form a x 10^{n }where n is a positive integer if the number is more than one and n is a negative integer if the number is less then one. 4583 in scientific notation would be: 4.583 x 10^{3} 0.000732 in scientific notation would be: 7.32 x 10^{4 }The decimal must always go after the first number and the n is the number of places you moved that decimal to put it after the first digit. 
score 
20 
SD 
see standard deviation 
sec 
the inverse of cos θ, sec θ = ^{1}/_{cos θ} 
secant 
a line which passes through at least two points of a curve or a circle 
sector 
the part of a circle between two radii and the circumference 
segment 
the part of a circle cut off by a chord 
selling price 
price a service or article is sold for 
semicircle 
half a circle 
septagon 
polygon with 7 sides (see also heptagon) 
sequence 
a set of numbers in a particular order or follow a particular pattern 
series 
the name given to the sum of numbers in a sequence (or pattern) 
set 
a group of clearly defined and identifiable members 
sexagesimal 
number system based on 60. Used for time and angles. On your calculator it is the ° ‘ ” button which stands for degrees, minutes and seconds 
sigma 
Greek letter, capital sigma: Σ denoting the sum of and little sigma: σ denoting the standard deviation usually, although it can also be used to denote an unknown angle 
sign 
the sign of a term tells us if it is positive or negative 
significant figures 
the number of figures that are important to a number. For example, 135836 correct to 2 significant figures would be 130000 
similar 
two shapes are similar if they are exactly the same shape, just not the same size 
similarity tests for triangles 
if all angles of one triangle are the same as the second triangle (AAA) or equiangular. If the sides about an equal angle are in equal ratio. If all side of one triangle are in equal ratio to the sides of the other triangle 
simple harmonic motion 
SHM, the motion of a body which oscillates. The formulas associated with SHM are x = acos(nt + α) or a = n^{2}x 
simple interest 
when money is invested and interest is only earned on the original amount invested. I = ^{PRN}/_{100 }where I is interest, P is principle invested, R is interest rate and N is the number of periods invested for 
simplify 
to answer a question in its most simple or basic form 
Simpson’s Rule 
used to find approximate areas of irregular shapes A = ^{h}/_{3}(d_{F} + 4d_{M} + d_{L}) (for use with General course) or
A =^{h}/_{3}{f(a) + f(b) + 4(sum of odd functions) + 2(sum of even functions)} (for use with Advanced course)

simultaneous 
occurring at the same time 
simultaneous equations 
two or more equations, solving them will give you the point of intersection between them 
sin 
sin θ = ^{opp}/_{hyp} 
sketch 
to draw without actually plotting 
skew distribution 
a distribution not symmetrical. The first diagram is an example of a positive skew. The ‘tail’ is being pulled in the positive direction (ie to the right). in the second diagram, the ‘tail’ is being pulled in a negative direction (ie left), so is negatively skewed 
skew lines 
lines that are not parallel, but do not intersect 
slant height 
the height from the vertex to the base edge of a pyramid or cone, not the perpendicular height. In this figure the slant height is represented by the letter L or s 
small circle 
circles drawn around the earth that do not pass through the centre. All circles of latitude, except the equator are small circles 
solid 
three dimensional shape 
solid of revolution 
shape formed when part of a line or curve is rotated about the x or y axis. V = π _{a}∫^{b} y^{2} dx if rotated about xaxis. V = π _{c }∫^{d} x^{2} dy if rotated about yaxis 
solution 
another name for the answer to a problem 
solve 
instruction to work out answer to question posed 
speed 
how much distance is covered in a certain time period. For example, 60km/h means for every hour travelled, 60km of distance will be covered 
sphere 
round solid shape, a ball $$V=\frac43\pi r^3$$ $$SA=4\pi r^2$$ 
spherical 
shaped like a sphere 
spread 
statistical term to measure how far from the average the data is. Measures of spread include the range, the interquartile range, the standard deviation 
square 
four sided shape with all sides equal, opposite sides parallel, adjacent sides perpendicular. Diagonals are equal and bisect at right angles 
square numbers 
1, 4, 9, 16, 25, 36, 49, 64, 81, 100…. 
square pyramid 
Solid shape with a square base and four triangular faces . 
square root 
to find the square root of a number we need to find a number that multiplies by itself to give us the number we want the square root of. For example 2 x 2 = 4, so the √4 = 2. 8 x 8 = 64, so the √64 = 8. 
standard deviation 
SD measures the spread of a distribution. Essentially, the larger the standard deviation, the more spread out, the smaller the standard deviation, the less spread out, or the more consistent the scores are 
stationary point 
the point on any curve where the tangent is parallel to the xaxis, having a gradient of zero. It is neither increasing, nor decreasing. Each stationary point must be either a maximum, minimum or a horizontal point of inflection. The stationary point can be found using ^{dy}/_{dx} = 0 (see also turning point) 
straight 
line that is not curved or bent 
straight angle 
angle of 180° 
subject 
the subject of an equation is the single letter that equals all the other terms. For example in y = 2x + 3z, y is the subject 
substitution 
replacing a letter in a formula with a number, another letter or another expression 
subtend 
is opposite to 
sum 
to add up, find the total of 
supplementary angles 
add to 180° 
surd 
a number with a root that cannot be simplified into a rational number. √12 may be simplified to 2√3, but no further. All surds are irrational numbers 
survey 
term in statistics when a portion of the population is tested, and that proportion is said to be representative of the whole population 
symbol 
sign or letter used to represent something else. The symbol = represents ‘equals’. The Greek symbol θ, theta, is used to represent unknown angles. 
symmetric 
having symmetry 
symmetry 
if you cut a shape in half, it will be the same on both sides 