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.