21-letter words containing p, r, o, v, i
- topological invariant — a property of a topological space that is a property of every space related to the given space by a homeomorphism.
- traveling salesperson — a representative of a business firm who travels in an assigned territory soliciting orders for a company's services.
- two-point perspective — a mathematical system for representing three-dimensional objects and space on a two-dimensional surface by means of intersecting lines that are drawn vertically and horizontally and that radiate from one point (one-point perspective) two points (two-point perspective) or several points on a horizon line as perceived by a viewer imagined in an arbitrarily fixed position.