AA Similarity: two triangles are similar if two corresponding angles are congruent. |

AAA similarity *see AA Similarity* |

A *see Ampere* |

AAS Congruence |

Abacus |

Abelian group *see Group* |

Abscissae *see Ordered Pair* |

Abscissa *see Ordered Pair* |

Absolute Convergence |

Absolute deviation *see Deviation* |

absolute error *see Measurement Error* |

Absolute frequency |

absolute magnitude *see Absolute Value* |

Absolute maximum *see Extremum* |

Absolute minimum *see Extremum* |

Absolute Value |

Absolute Value Classroom Demonstrator |

Absurd |

Abundant Number |

Acceleration |

Accumulation factor *see Interest* |

accuracy *see Measurement Error* |

acre *see Area* |

actual value *see Measurement Error* |

Acute Angle |

Acute scalene triangle *see Acute Triangle* |

Acute Triangle |

addend *see Addition* |

Adding rational expressions *see Rational Expression* |

Addition |

addition facts *see Addition* |

addition of complex numbers *see Complex Number* |

Addition of fractions *see Operations on Fractions* |

Addition of functions *see Function* |

Addition of Integers Classroom Demonstrator |

addition of matrices *see Matrix* |

Addition of matrix rows *see Using Matrices to Solve Linear Systems* |

Addition of polynomials *see Polynomial* |

Addition of Real Numbers Classroom Demonstrator |

addition postulate *see Angle* |

Addition property of equality *see Equal* |

addition sign *see Addition* |

Addition using scientific notation *see Scientific notation* |

Addition, commutative property of *see Commutative Property of Addition* |

addition, vector *see Vector* |

Additive Identity |

Additive Inverse |

Additive Property of Equality |

additive property of zero *see Addition* |

Adjacent |

Adjacent arcs *see Arc* |

Aleph null |

Algebra |

Algebra Tiles |

Algebra, Boolean *see Boolean Algebra* |

Algebra, fundamental theorem of *see Fundamental Theorem of Algebra* |

Algebraic |

Algebraic representation *see Algebraic* |

Algorithm |

Alternate Angles |

Alternate Exterior Angles Theorem |

Alternate exterior angles *see Alternate Angles* |

Alternate Interior Angles Theorem |

Alternating Series |

Altitude |

Altitude of a triangle *see Triangle* |

amp *see Ampere* |

Ampere |

Amplitude |

Analytic Geometry |

Analytic Values of Trigonometric Functions *see Exact Values of Trigonometric Functions* |

Analytical proof |

And rule *see Logical Argument* |

And *see Conjunction* |

Angle |

Angle Addition Postulate *see Angle* |

angle bisector *see Angle* |

Angle Class Classroom Demonstrator |

angle measure *see Angle* |

Angle of Depression *see Angle of Elevation and Depression* |

Angle of Elevation and Depression |

Angle of Repose |

Angle of rotation *see Rotation* |

Angle Sum Theorem *see Triangle* |

Angle, dihedral *see Dihedral Angle* |

Angle, right *see Right Angle* |

angle-angle similarity *see AA Similarity* |

angle-angle-angle similarity *see AA Similarity* |

angle-angle-side congruence *see AAS Congruence* |

Annual interest rate *see Interest* |

Annualize *see Interest* |

Annulus |

Antecedent *see Implication* |

anticlockwise *see Clockwise* |

Antipodal |

Apex |

Apothem |

Apply |

Approximate |

approximately *see Approximate* |

Arabic Numerals |

Arbitrary |

Arc |

Arc length *see Arc* |

Arc of a chord *see Chord* |

arccos *see Arccosine* |

Arccosecant |

Arccosine |

Arccotangent |

arccot *see Arccotangent* |

arccsc *see Arccosecant* |

Area |

Area of a triangle *see Triangle* |

Area, circle *see Circle* |

Area, ellipse *see Ellipse* |

Area, parallelogram *see Parallelogram* |

Area, rectangle *see Rectangle* |

argand diagram *see Complex Number* |

Argument, logical *see Logical Argument* |

Argument, valid *see Valid Argument* |

Arithmetic |

Arithmetic average *see Arithmetic Mean* |

Arithmetic Fact |

Arithmetic fact *see Arithmetic Fact* |

arithmetic growth *see Growth* |

Arithmetic Mean |

Arithmetic Precision |

arithmetic progression *see Arithmetic Sequence* |

Arithmetic Sequence |

Arithmetic Series |

arrow (vector) *see Vector* |

ASA Congruence |

Associative |

Associative Property of Addition |

Associative Property of Multiplication |

Assumption |

Asymptote |

atto- *see International System of Units* |

augmented matrix *see Matrix* |

Average |

Average absolute deviation *see Deviation* |

Average Rate of Change |

Axiom |

Axiom of Choice |

Axiom of parallels *see Parallel Postulate* |

axiomatic system *see Axiom* |

Axis |

Axis of an ellipse *see Ellipse* |

Axis of reflection *see Reflection* |

Axis of rotation *see Axis* |

Axis of symmetry *see Axis* |

axis, imaginary *see Complex Number* |

axis, real *see Complex Number* |