simplex

Everyday

1. (technical) Simple, made of one part; not compound. tree →
2. (communication) A simplex link sends messages in only one direction, like a radio broadcast (unlike duplex, which goes both ways). tree →
3. (maths) A simplex is the simplest shape in any number of dimensions: a point, a line segment, a triangle, a tetrahedron. tree →
4. (medicine) In "herpes simplex", the name of the virus that causes cold sores. tree →

In the lessons

In maths, a triangle is a 2-dimensional simplex and a tetrahedron (a triangle-based pyramid) is a 3-dimensional one. In computing and science, "simplex" describes one-way communication. In health, herpes simplex causes cold sores. Most pupils will meet the word only in these technical uses. Phrases: simplex method (a maths way to solve problems), herpes simplex, simplex communication.

Examples

• A triangle is a simplex in two dimensions. tree →
• A TV broadcast is simplex: it only goes one way. tree →
• Cold sores are caused by herpes simplex virus. tree →
• A tetrahedron is a three-dimensional simplex. tree →
• Walkie-talkies are half-duplex, not simplex. tree →
• The simplex method helps factories plan their work. tree →

Note

A technical word, not used in everyday speech. Plural: simplexes or simplices. Opposite in communication: duplex (two-way). "Simplex" is Latin for simple.