Triangular baseOne of the two triangles at the ends. The two bases are parallel and the same size, and the prism is named for them.
Lateral faceOne of the three faces that join the bases. On a right prism each is a rectangle. Two are behind here.
Base edgeA side of one of the triangular bases. There are six base edges, three on each base.
Lateral edgeAn edge where two lateral faces meet. The three lateral edges run from base to base and are equal in length.
VertexA corner where three edges meet. Six vertices on a triangular prism, three on each base.
The net 3
NetThe prism unfolded and laid flat. It has three rectangles and two triangles, and it folds along the dashed lines.
Length of the prismThe distance between the two triangular bases. It is also called the height, or altitude, of the prism.
Height of the triangleThe line from one corner straight to the opposite side. It meets that side at a right angle.
How this list was compiled: Every name was read on 2026-10-03 in at least two of these. (1) Wikipedia, English edition, Triangular prism, https://en.wikipedia.org/wiki/Triangular_prism (a prism with two triangular bases; six vertices, nine edges and five faces; the bases congruent; rectangular lateral faces on a right prism; the base's edges; the base b and height h of the triangle and the distance l between the two triangular bases; the net), Prism (geometry), https://en.wikipedia.org/wiki/Prism_(geometry) (prisms named after their bases; the height as the distance between the two base faces; a right prism), and Net (polyhedron), https://en.wikipedia.org/wiki/Net_(polyhedron) (edge-joined polygons in the plane that fold along edges into the faces of the polyhedron; many different nets for one polyhedron). (2) George Wentworth and David Eugene Smith, Solid Geometry, 1911, public domain, https://archive.org/details/wentworthssolidg00wentrich, sections 500 to 507 (faces, edges and vertices of a polyhedron; the bases, lateral faces and lateral edges of a prism; the lateral edges equal; the altitude; the right prism; triangular prisms; the base edge and the sides of the base in the exercises). (3) A school mensuration text of 1893, public domain, https://archive.org/details/mensuration00hallgoog, read by full-text search (a triangular prism whose length is given; lateral edges; the altitude of a triangle drawn perpendicular to its base). (4) California Department of Education, California Common Core State Standards: Mathematics, https://www.cde.ca.gov/be/st/ss/documents/ccssmathstandardaug2013.pdf (grade 6: three-dimensional figures represented by nets made up of rectangles and triangles). Hints, detail lines and the order are our own. Licence: own work
The drawing: Drawn for this site by script, 2026-10-03, from plain geometry. Own work. Licence: own work
How it works
This triangular prism labeled drawing names the triangular bases, lateral faces, base edges, lateral edges and vertices. The second drawing is a triangular prism net labeled with the length of the prism and the height of its triangle.
Read the full guide
The prism
Numbers 1 to 5 are on the prism. The two triangles at the ends are the bases, and the three rectangles that join them are the lateral faces. A base edge is a side of a triangle. A lateral edge runs from one base to the other. Dashed lines are the edges at the back.
The net
Numbers 6 to 8 are on the net: the same prism unfolded into three rectangles and two triangles. It folds along the dashed lines. The arrow at the side is the length of the prism, and the dotted line in the triangle is its height.
Count to check a drawing of a triangular prism: five faces, nine edges, six vertices.
Questions and answers
How many faces, edges and vertices does a triangular prism have?
Five faces, nine edges and six vertices. Two of the faces are the triangular bases and three are lateral faces. Six of the edges are base edges and three are lateral edges.
What is the net of a triangular prism?
The five faces of the prism unfolded and laid flat: three rectangles and two triangles joined along their edges. Folded along those edges it makes the prism. One prism has more than one net, depending on which edges are cut.
What are the bases of a triangular prism?
The two triangles. They are parallel and the same size, and the prism is named for them. A base is not always the face a prism rests on: the prism drawn here lies on a rectangle.
What is a lateral face of a prism?
A face that joins the two bases. A triangular prism has three. On a right prism, where the lateral edges are perpendicular to the bases, every lateral face is a rectangle.