# On

**On Line Test Equipment**- Continuously monitors the performance of electronic systems.
**On This Day**- Events in science and engineering that happened on a particular day.
**One Dimensional**- Having length, but no width e.g. a line.
**One to One**- A function f is said to be one to one if f(x)=f(y) implies that x=y.
**onto**- A function f is said to map A onto B if for every b in B, there is some a in A such f(a)=b.