Conjugate, from L. conjungo, to yoke or join together ; from L. con, together;

and L. jugum, that which joins, a yoke. Converge, from F. converger, L. con -- with; L. vergo, to bend, or incline. Co-ordinate, from L. Co (con), together; and L. ordo, inis, a straight row, a

regular series. Cube, from L. cubus ; G. kubos, a die. Curve, from L. curvus, a, um, crooked, bent. Cylinder, from G. kylindros; from G. kylindo, to roll. Hence roller-like.

Decagon, from G. deka, ten ; and G. gònia, an angle (corner).
Decimal, from L. decem, ten.
Diagonal, from G. diagonios, from corner to corner. [G. dia, through; and

G. gônia, a corner.]
Diagram, from G. diagramma, that which is marked out by lines ; from G.

dia, round; and G. graphò, to write or delineate. Diameter, from G. diametros, measurement through ; from G. dia, through ;

and G. metrun, a measure. Dihedral, from G. di, double ; and G. hedra, a base. Dodecagon, from G. dõdeka, twelve ; and G. gônia, an angle (corner). Dodecahedron, from G. dõdeka, twelve; and G. hedra, a base. Duodecimal, from L. duodecim, twelve. [L. duo = two, and L. decem =

ten.]

Elevation, from L. elevo, to lift up or raise ; from L. e, up; and L. levo, to

raise. Ellipse, from G. elleipsis, a defect or leaving out. [G. elleipo, to leave out.) Equilateral, from L. aequilaterus, equal-sided; from L. aequus, a, um, equal;

and L. latus, lateris, a side. Equivalent, from L. aequus, a, um, equal; and L. valens, valentis, being

strong. [L. valeo = to be strong.]

Hypotenuse, from G. hypoteinousa, the line subtending a right angle; from

G. hypo, under; and G. teino, to stretch.

Icosahedron, from G. eikosi, twenty; and G. hedra, a base.
Intersect, from L. inter, between; and L. seco (sectum), to eut.
Involute, from L. involvo, to roll around, wrap up; fronı L. in, upon; and

L. volvo, volutum, to roll.
Isosceles, from G. isoskelēs, having equal legs; from G. isos, equal; and G.

skelos, a leg.

Line, from L. linea, a linen thread. [L. linum = flax.]

Multilateral, from L. multilaterus, many-sided ; from L. multus, a, um,

many; and L. latus, lateris, a side.

Nonagon, from L. nonus, a, um, the ninth; and G. gònia, a corner.

Parabola, from G. parabolē, a placing beside ; from G. para, from, by the

side of; and G. ballo, to throw. Parallel, from G. para, by the side of; and G. allelos, one another. [G.

allos = another.] Parallelogram, from G. parallēlogrammon, a figure bounded with parallel

sides. [G. grammē = a line.] Penetration, from L. penetro (penetratum), to place or set into. Pentagon, from G. pente, five; and G. gônia, a corner. Perimeter, from G. peri, around; and G. metron, a measure. Periphery, froin G. peri, around; and G. phero, to carry. Perpendicular, from L. perpendiculum, a plumb - line; from L. per,

thoroughly ; and L. pendo, to weigh. Plane, from L. planus, perfectly flat. Point, from L. punctum, a point, or small hole. [L. pungo = to pierce

into ] Polygon, from G. polugonos, a figure having many angles ; from G. polus,

many; and G. gònia, a corner. Prism, from G. prisma. [G. prizo = to saw.]

Problem, from G. problēma, that which is proposed; from G. pro, before ;

and G. ballo, to throw. Profile, from L. pro, forth; and L. filum, a thread. Projection, from L. projicio (projectum), to throw forth or before ; from

L. pro, forth; and L. jaceo, to throw. Proportional, from L. proportio, symmetry, analogy; from L. pro, in com

parison with ; and L. portio, portionis, part, share. Pyramid, from G. pyramis, pyramidos, usually derived from G. pyr, a flame,

because of its pointed shape.

Quadrant, from L. quadrans, -antis, making square ; from L. quadro, to make

square. [L. quatuor = four.] Quadrilateral, from L. quadrilaterus, four-sided; from L. quatuor, four; and

L. latus, lateris, a side.
Quatrefoil, from F. quatre, four; and F. feuille, a leaf.

Radius, from L. radius, a spoke of a wheel.
Ratio, from L. ratio, calculation. [L. reor (ratus), to think, suppose.]
Rectangle, from L. rectus, a, um, right; and L. angulus, a corner.
Rectilineal, from L. rectus, a, um, right, straight; and L. linea, a linen

thread. [L. linum = flax.] Rhombus, from G. rhombos, a wheel thus shaped, and turned on a pivot.

[G. rhembo, to turn round and round.]. Rhomboid, from G. rhombos, and G. eidos, form, shape.

Scale, from L. scala, a ladder, flight of steps. [L. scando, to mnount.]
Scalene, from G. skalēnos, unequal, uneven. [G. skaző, to limp.]
Sector, from L. sector, one who cuts. [L. seco (sectum), to cut.]
Segment, from L. segmentum, a piece cut off. [L. seco (sectum), to cut.]
Semi-circle, from L. semi, half; and L. circulus, a ring; from G. kirkos,

a circle.
Sphere, from G. sphaira, a ball or globe.
Spiral, from G. speira, anything wound round, a coil.
Square, from L. quadro, to make square. [Old F. esquarré, a square ;

modern F. carré, square.] Superficies, from L. superficies, the upper side, the top; from L. super,

above; and L. facies, a face.

Tangent, from L. tangens, -entis, touching. (L. tango = to touch.]
Tetrahedron, from G. tetra, four; and G. hedra, a base.
Trace, from L. traho, to draw. [F. trace = trace.]
Transverse, from L. transversus, lying across ; from L. trans, across; and

L. verto (versum), to turn.

Trapezium, from G. trapezion, dim. of trapeza, a table; contracted either

from G. tri-peza, three-legged; or from G. tetra-peza, four-legged. Trapezoid, from G. trapezion, and G. eidos, shape, form. Trefoil, from F. trois, three; and F. feuille, a leaf. Triangle, from L. triangulus, having three corners; from L. tres, three; and

L. angulus, a corner.
Trilateral, from L. trilaterus, having three sides; from L. tres, three ; and

L. latus, lateris, a side.
Trisect, from L. tres, three; and L. seco (sectum), to cut.

Vertex, from L. vertex, the top or crown of the head. [L. verto = to turn.]
Vertical, from L. vertex (verticis), the top of the head.
Volute, from L. volvo (volutum), to roll.

INDEX TO PROBLEMS IN PLANE GEOMETRY.

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Altitude; to find, of given triangle, ... ...
Angle; to bisect,
- of 45°; to construct, on given line, ...
- of 60°, 30°, or 15°; to construct, on given line,
- ; to make, equal to given angle, from given point, in the given

line, ... ... ... ... ... ... ...
— ; to make, equal to given angle, from given point, outside the

given line, ... ... ... ... ... :
- ; to bisect, made by two converging lines, the angular point

being inaccessible; ...
--, right, to trisect, ... ...
Arc; to bisect, ... ...
- tangential; to draw, to two given circles, touching one of the

given ciroles in a given point, ...
- of a circle; to describe, tangential to two given converging

lines, ... ... ... ... ... ...
— ; to describe, tangential to given arc and given line, ...
Circle; to find centre of,
- ; to describe, passing through three given points, ...
- ; to describe, passing through given point, and tangential to

given line, ..
—; to describe, touching two given circles, ...

; to describe, of given radius, touching two given circles,
; to inscribe, within given triangle, ...
; to inscribe, within given square, ...
; to inscribe, within given rhombus,
; to inscribe, within given trapezium,
.; to inscribe, within given quadrant,
- ; to describe, about given triangle, ...

-; to describe, about given square, ...
-; to construct, two-thirds of given circle, ...
—; to describe, of given radius, tangential to two converging lines,

; to draw, touching given circle in given point, also a given line,

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