# Symbols:Abbreviations

## A

### AAS

Triangle Angle-Angle-Side Congruence.

### AC

The Axiom of Choice.

Same as AoC.

### ACC

The Axiom of Countable Choice.

The Axiom of Dependent Choice.

### a.e. or AE

Abbreviation for almost everywhere.

### agm

Abbreviation for arithmetic-geometric mean.

### AH

Abbreviation for aleph hypothesis.

### alg.

Abbreviation for algebra or algebraic.

### ANOVA

Abbreviation for analysis of variance.

### AoC

The Axiom of Choice.

Same as AC.

### A.P.

Abbreviation for arithmetic progression (or arithmetical progression).

### arith.

Abbreviation for arithmetic or arithmetical.

### ASA

Triangle Angle-Side-Angle Congruence.

### ASCII

Acronym for American Standard Code for Information Interchange.

### avdp.

Abbreviation for avoirdupois.

## B

### BIBD

Balanced incomplete block design.

### BNF

Backus-Naur Form (previously Backus normal form until the syntax was simplified by Peter Naur).

It was Donald Knuth who suggested the name change, on the grounds that "normal" is an inaccurate description.

### BPI

The Boolean Prime Ideal Theorem.

## C

### cdf or c.d.f.

Cumulative distribution function.

Let $\struct {\Omega, \Sigma, \Pr}$ be a probability space.

Let $X$ be a real-valued random variable on $\struct {\Omega, \Sigma, \Pr}$.

The cumulative distribution function of $X$ is denoted $F_X$, and defined as:

$\forall x \in \R: \map {F_X} x := \map \Pr {X \le x}$

### CH

Continuum Hypothesis.

Center of mass.

### CNF or cnf

Conjunctive normal form.

### CPA

Critical path analysis.

Cumulative sum.

See cusum chart.

## D

### D.C.

Differential Coefficient:

Some sources refer to a derivative as a differential coefficient, and abbreviate it D.C.

Some sources call it a derived function.

Such a derivative is also known as an ordinary derivative.

This is to distinguish it from a partial derivative, which applies to functions of more than one independent variable.

In his initial investigations into differential calculus, Isaac Newton coined the term fluxion to mean derivative.

### DCC

Descending chain condition

Declination

### DES

Data encryption standard

### d.f.

Degrees of freedom

### d.f.

Rarely: distribution function.

The abbreviation c.d.f. for cumulative distribution function is preferred.

### DNF or dnf

Disjunctive normal form.

### d.o.f.

Degrees of freedom

### D.S.

Disjunctive Syllogism, also known as Modus Tollendo Ponens.

## E

### EDA

Exploratory data analysis.

Exploratory data analysis is the process of performing preliminary examination of raw data in order to gain insight into their general structure and characteristics, and often identify outliers.

Tools used in this activity include:

For multivariate data or particularly large data sets, kernel density estimation methods can be used.

Having performed an exploratory data analysis, the data engineer may be better placed to make a decision as to what formal statistical methods may then be appropriate.

### EE

Context: Predicate Logic.

Rule of Existential Elimination, which is another term for the Rule of Existential Instantiation ($\text {EI}$).

### EG

Context: Predicate Logic.

Rule of Existential Generalisation.

### EI

Context: Predicate Logic.

Rule of Existential Instantiation.

Alternatively, Rule of Existential Introduction, which is another term for the Rule of Existential Generalisation ($\text {EG}$). Beware.

### essup

Essential supremum.

Let $\struct {X, \Sigma, \mu}$ be a measure space.

Let $f : X \to \R$ be an essentially bounded function:

$\map \mu {\set {x \in X : \size {\map f x} > c} } = 0$

The essential supremum of $\size {\map f x}$ is the supremum of all possible $c$, and is written $\essup \size {\map f x}$.

### EMF

Context: Electromagnetism.

Electromotive force.

Electromotive force is a quantity that measures the source of potential energy in an electric circuit.

It is defined as the amount of work per unit electric charge.

## F

### FCF

Finite continued fraction.

### FFT

Fast Fourier transform.

## G

### GCD or g.c.d.

Greatest common divisor.

Also known as:

highest common factor (hcf or h.c.f.)
greatest common factor (gcf or g.c.f.)

### GCF

Greatest common divisor.

Also known as:

greatest common factor (GCD, gcd or g.c.d.)
highest common factor (HCF, hcf or h.c.f.)

### GCH

The Generalized Continuum Hypothesis can be abbreviated $\operatorname {GCH}$.

### glb

Greatest lower bound.

Another term for infimum.

### G.P.

Geometric progression.

## H

Hour angle.

### HCF or h.c.f.

Highest common factor.

Also known as greatest common divisor (g.c.d.).

Hypotenuse.

Hypothesis.

## I

If and only if.

### ICF

Infinite continued fraction.

### ICM

International Congress of Mathematicians.

### ISBN

International Standard Book Number.

### I.V.P.

#### I.V.P.: 1

The intermediate value property.

#### I.V.P.: 2

An initial value problem.

## L

### LCD

The lowest (or least) common denominator.

### LCM, lcm or l.c.m.

The lowest (or least) common multiple.

### LHS

Left hand side.

In an equation:

$\text {Expression$1$} = \text {Expression$2$}$

the term $\text {Expression$1$}$ is the left hand side.

### LQR

Let $p$ and $q$ be distinct odd primes.

Then:

$\paren {\dfrac p q} \paren {\dfrac q p} = \paren {-1}^{\dfrac {\paren {p - 1} \paren {q - 1} } 4}$

where $\paren {\dfrac p q}$ and $\paren {\dfrac q p}$ are defined as the Legendre symbol.

An alternative formulation is: $\paren {\dfrac p q} = \begin{cases} \quad \paren {\dfrac q p} & : p \equiv 1 \lor q \equiv 1 \pmod 4 \\ -\paren {\dfrac q p} & : p \equiv q \equiv 3 \pmod 4 \end{cases}$

The fact that these formulations are equivalent is immediate.

This fact is known as the Law of Quadratic Reciprocity, or LQR for short.

### lsb or l.s.b.

Least significant bit.

### LSC

Lower semicontinuous.

## M

### MGF or M.G.F.

Moment generating function.

Modus Ponens.

### msb or m.s.b.

Most significant bit.

## N

### NNF

Negation normal form.

### N.P.D.

North polar distance.

## O

### ODE

Ordinary differential equation.

## P

### PBD

Pairwise balanced design.

### PCI

Principle of Complete Induction (or Principle of Complete Finite Induction).

### PCFI

Principle of Complete Finite Induction.

### PDE

Partial differential equation.

A partial differential equation is a differential equation which has:

one dependent variable
more than one independent variable.

The derivatives occurring in it are therefore partial.

### pdf

Probability density function:

Let $\struct {\Omega, \Sigma, \Pr}$ be a probability space.

Let $X$ be an absolutely continuous random variable on $\struct {\Omega, \Sigma, \Pr}$.

Let $P_X$ be the probability distribution of $X$.

Let $\map \BB \R$ be the Borel $\sigma$-algebra of $\R$.

Let $\lambda$ be the Lebesgue measure on $\struct {\R, \map \BB \R}$.

We define the probability density function $f_X$ by:

$\ds f_X = \frac {\d P_X} {\d \lambda}$

where $\dfrac {\d P_X} {\d \lambda}$ denotes the Radon-Nikodym derivative of $P_X$ with respect to $\lambda$.

### PERT

Program Evaluation and Review Technique.

### PET

Principle of the Excluded Third.

### PFI

Principle of Finite Induction.

### PGF or p.g.f.

Probability generating function:

Let $X$ be a discrete random variable whose codomain, $\Omega_X$, is a subset of the natural numbers $\N$.

Let $p_X$ be the probability mass function for $X$.

The probability generating function for $X$, denoted $\map {\Pi_X} s$, is the formal power series defined by:

$\ds \map {\Pi_X} s := \sum_{n \mathop = 0}^\infty \map {p_X} n s^n \in \R \sqbrk {\sqbrk s}$

### PID or pid

Principal ideal domain:

A principal ideal domain is an integral domain in which every ideal is a principal ideal.

### PMF, pmf or p.m.f.

Probability mass function:

Let $\struct {\Omega, \Sigma, \Pr}$ be a probability space.

Let $X: \Omega \to \R$ be a discrete random variable on $\struct {\Omega, \Sigma, \Pr}$.

Then the probability mass function of $X$ is the (real-valued) function $p_X: \R \to \closedint 0 1$ defined as:

$\quad \forall x \in \R: \map {p_X} x = \begin {cases} \map \Pr {\set {\omega \in \Omega: \map X \omega = x} } & : x \in \Omega_X \\ 0 & : x \notin \Omega_X \end {cases}$

where $\Omega_X$ is defined as $\Img X$, the image of $X$.

That is, $\map {p_X} x$ is the probability that the discrete random variable $X$ takes the value $x$.

### PMI

Principle of Mathematical Induction.

### PNT

Prime Number Theorem.

### Poset

Partially Ordered Set.

A partially ordered set is a relational structure $\struct {S, \preceq}$ such that $\preceq$ is a partial ordering.

The partially ordered set $\struct {S, \preceq}$ is said to be partially ordered by $\preceq$.

## Q

### QED

Quod Erat Demonstrandum

The initials of Quod Erat Demonstrandum, which is Latin for which was to be demonstrated.

These initials were traditionally added to the end of a proof, after the last line which is supposed to contain the statement that was to be proved.

### QEF

Quod Erat Faciendum

The initials of Quod Erat Faciendum, which is Latin for which was to be done.

These initials were traditionally added to the end of a geometric construction.

### QEI

Quod Erat Inveniendum

The initials of Quod Erat Inveniendum, which is Latin for which was to be found.

These initials were traditionally added after the completion of a calculation (either arithmetic or algebraic).

## R

### RHS

Right hand side.

In an equation:

$\text {Expression$1$} = \text {Expression$2$}$

the term $\text {Expression$2$}$ is the right hand side.

### RHS

Triangle Right-Angle-Hypotenuse-Side Congruence.

### Reduced Echelon Form

ref is an abbreviation for reduced echelon form.

rref is an abbreviation for reduced row echelon form.

The matrix $\mathbf A$ is in reduced echelon form if and only if, in addition to being in echelon form, the leading $1$ in any non-zero row is the only non-zero element in the column in which that $1$ occurs.

Such a matrix is called a reduced echelon matrix.

## S

### SAA

Triangle Side-Angle-Angle Congruence.

### SAS

Triangle Side-Angle-Side Congruence.

### SCF

Simple continued fraction.

### SFCF

Simple finite continued fraction.

### SHM

Simple harmonic motion.

### SICF

Simple infinite continued fraction.

### SSS

Triangle Side-Side-Side Congruence.

### SUVAT

A category of problems in elementary applied mathematics and Newtonian physics involving a body $B$ under constant acceleration $\mathbf a$.
They consist of applications of the equations:

Let $B$ be a body under constant acceleration $\mathbf a$.

The following equations apply:

### $(1):$ Velocity after Time

$\mathbf v = \mathbf u + \mathbf a t$

### $(2):$ Distance after Time

$\mathbf s = \mathbf u t + \dfrac {\mathbf a t^2} 2$

### $(3):$ Velocity after Distance

$\mathbf v \cdot \mathbf v = \mathbf u \cdot \mathbf u + 2 \mathbf a \cdot \mathbf s$

where:

$\mathbf u$ is the velocity at time $t = 0$
$\mathbf v$ is the velocity at time $t$
$\mathbf s$ is the displacement of $B$ from its initial position at time $t$
$\cdot$ denotes the dot product.

The term SUVAT arises from the symbols used, $\mathbf s$, $\mathbf u$, $\mathbf v$, $\mathbf a$ and $t$.

## U

### UE

Universal Elimination (another name for Universal Instantiation: UI).

### UF

Ultrafilter Lemma (also UL).

### UFD

Unique factorization domain.

### UI

Universal Instantiation.

### UL

Ultrafilter Lemma (also UF).

### URM

Unlimited register machine: an abstraction of a computing device with certain particular characteristics.

## W

### WFF or wff

Well-formed formula.

### WLOG

Without loss of generality.

Suppose there are several cases which need to be investigated.

If the same argument can be used to dispose of two or more of these cases, then it is acceptable in a proof to pick just one of these cases, and announce this fact with the words: Without loss of generality, ..., or just WLOG.

### WRT or w.r.t.

(Differentiation) with respect to.

When performing calculus operations, that is differentiation or integration, one needs to announce which variable one is "working with".

Thus the phrase with respect to is (implicitly or explicitly) part of every statement in calculus.

## Z

### ZF

An abbreviation for Zermelo-Fraenkel Set Theory, a system of axiomatic set theory upon which most of conventional mathematics can be based.

### ZFC

An abbreviation for Zermelo-Fraenkel Set Theory with the Axiom of Choice, a system of axiomatic set theory upon which the whole of (at least conventional) mathematics can be based.