Line segmentA straight piece of a line between two endpoints.
EndpointA point where a segment ends. A ray has one endpoint, where it starts.
LineA straight path that goes on in both directions. It has no endpoints.
RayPart of a line with one endpoint. It goes on without end in one direction.
PointAn exact position, drawn as a dot. It has no size.
MidpointThe point half way between the two endpoints. M is the midpoint of segment JK.
ArrowheadIt shows that the line goes on without end.
How it is written 5
Segment symbolA bar over the letters of the two endpoints.
Line symbolA two-headed arrow over the letters of two points on the line.
Ray symbolA one-headed arrow over two letters. The endpoint's letter comes first.
Point nameOne capital letter, written beside the dot.
Tick marksMatching marks show segments of the same length. Here JM and MK are equal.
How this list was compiled: Every name and every way of writing was read on 2026-10-03 in at least two of these. (1) Wikipedia, English edition: Line segment, https://en.wikipedia.org/wiki/Line_segment (a part of a straight line bounded by two distinct endpoints; often denoted using an overline above the symbols for the two endpoints); Line (geometry), https://en.wikipedia.org/wiki/Line_(geometry) (a line is infinitely long; a ray, or half-line, starts at its initial point and proceeds indefinitely in one direction only); Midpoint, https://en.wikipedia.org/wiki/Midpoint (the middle point of a line segment, equidistant from both endpoints); Hatch mark, https://en.wikipedia.org/wiki/Hatch_mark (hatch marks, also called tick marks; matching hatch marks indicate equal lengths). (2) Math is Fun, Symbols in Geometry, https://www.mathsisfun.com/geometry/symbols.html, and Line in Geometry, https://www.mathsisfun.com/geometry/line.html (the line segment symbol is a bar over the letters AB, the ray symbol a bar with one arrow, the line symbol a bar with arrows at both ends; a line extends in both directions without end; with ends it is a line segment, with just one end a ray; a point has no dimensions, only position). (3) California Department of Education, California Common Core State Standards: Mathematics, https://www.cde.ca.gov/be/st/ss/documents/ccssmathstandardaug2013.pdf, read with pdftotext (grade 4: draw points, lines, line segments, rays; two rays share a common endpoint; the endpoints of a segment). (4) Geometry Success in 20 Minutes a Day (2010), https://archive.org/details/geometrysuccessi0000unse, read by full-text search (a line named by two points on it under a small symbol of a line with two arrowheads; a line has no endpoints and a ray has one; for a ray the endpoint is always named first, so ray AB is not ray BA). (5) Modern Mathematics for the Junior High School, Geometry 1 (1966), https://archive.org/details/ERIC_ED040875 (the arrowheads on the line AB tell us that the line goes on infinitely in both directions; a line has no endpoint), and Mathematics 7th Year, Part 1 (1966), https://archive.org/details/ERIC_ED025422 (a point is represented by a dot and named by a capital letter placed near the dot; a line has no endpoints, a line segment has two). (6) Circles and Spheres (2007), https://archive.org/details/circlesspheres0000leec (a point is named using a capital letter). (7) Basic Algebra and Geometry (1990), https://archive.org/details/basicalgebrageom01albe_0 (a ray is named by stating the endpoint first). (8) Basic Geometry for College Students (2003), https://archive.org/details/basicgeometryfor0000tuss (line segment AB written with a bar; every line segment has a midpoint), and a state test workbook of 2007 read by full-text search, https://archive.org/details/buckledownnewyor0000unse (congruent segments have equal lengths; matching sides are shown using tick marks). Hints, detail lines and the order are our own. Licence: own work
The drawing: Drawn for this site by script, 2026-10-03. Own work. Licence: own work
How it works
A chart for labeling lines and line segments, rays and points. The first view names each figure with its endpoints, midpoint and arrowheads. The second shows how each is written: a capital letter, a bar, an arrow and tick marks.
Read the full guide
The figures
A point is drawn as a dot. A line goes on without end in both directions, so it has an arrowhead at each end and no endpoints. A line segment stops at two endpoints. A ray starts at one endpoint and goes on in one direction. M, the midpoint, is half way between J and K.
How each is written
A point is named with one capital letter. A line, a line segment and a ray each take two letters, and the mark over the letters says which is meant: a two-headed arrow, a bar or a one-headed arrow.
Segment DE and segment ED are the same segment. For a ray the order matters: the endpoint's letter comes first.
Questions and answers
How do you label a line segment?
Name it with the capital letters of its two endpoints and draw a bar over them. The segment from D to E is written DE with a bar on top.
What is the difference between a line, a line segment and a ray?
A line goes on without end in both directions and has no endpoints. A line segment is the part of a line between two endpoints. A ray has one endpoint and goes on without end in one direction.
How do you name a ray?
Write the letter of the endpoint first, then the letter of another point on the ray, under an arrow with one head. Ray FG starts at F and passes through G.
What do tick marks on a line segment mean?
Matching tick marks show that segments have the same length. On this chart each half of segment JK has one tick mark, because M is its midpoint.