Geometry: Fundamentals of Points, Lines, Angles, and Midpoints

Vocabulary flashcards covering foundational geometric terms from Lessons 2.1, 2.2, and 2.3, including lines, segments, rays, midpoint coordinates, and angle classifications.

Point

A precise location in space represented by a dot and named with a single capital letter, such as Point $A$.

Line Segment ($\overline{AB}$)

A measurable part of a line bounded by two distinct endpoints; the order of the letters does not matter ($\overline{AB}$ is the same as $\overline{BA}$) because it has no direction.

Ray ($\overrightarrow{AB}$ )

A part of a line that begins at a specific endpoint and extends infinitely in one direction; the order of the letters matters because the first letter must name the initial endpoint.

Line ($\overleftrightarrow{AB}$)

A straight geometric figure that extends infinitely in two opposite directions without endpoints; it has no length or direction, so the order of the points in its notation does not matter.

Segment Length ($AB$)

The numerical distance between two endpoints $A$ and $B$, denoted without a bar above the letters.

Congruent ($\cong$)

A relationship between geometric figures indicating that they have the exact same size, shape, or measure.

Perpendicular ($\perp$)

A geometric relationship where two lines, rays, or segments intersect to form a right angle ($90^\circ$).

Parallel ($\parallel$)

A geometric relationship describing coplanar lines that go in the exact same direction and never intersect.

Bisect

To divide or cut a geometric figure (such as a segment or an angle) into two equal or congruent halves.

Midpoint

The point on a segment that is located exactly halfway between its two endpoints, cutting the segment into two congruent halves.

Midpoint Formula

The algebraic method used to calculate the coordinates of the midpoint between two endpoints $(x_1, y_1)$ and $(x_2, y_2)$: $M = \left(\frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2}\right)$, which averages the $x$-coordinates and $y$-coordinates.

Equidistant

Being at an equal distance from two or more points, locations, or geometric objects.

Angle

A geometric figure formed by two rays that share a common endpoint called the vertex.

Vertex

The shared endpoint where the two rays of an angle meet.

Angle Bisector

A ray that divides an angle into two congruent angles of equal measure.

Adjacent Angles

Two angles that share a common vertex and a common side (ray) without overlapping.

Acute Angle

An angle whose measure is strictly greater than $0^\circ$ and strictly less than $90^\circ$.

Right Angle

An angle whose measure is exactly equal to $90^\circ$.

Obtuse Angle

An angle whose measure is strictly greater than $90^\circ$ and strictly less than $180^\circ$.

Straight Angle

An angle whose measure is exactly equal to $180^\circ$, forming a straight line.

Complementary Angles

Two angles whose degree measures add up to a sum of exactly $90^\circ$.

Supplementary Angles

Two angles whose degree measures add up to a sum of exactly $180^\circ$.