boundary

Psychologists tell us boundaries are healthy…. But few boundaries remain.

frontier

We may use robots to expand our frontiers, first through their ability to withstand environments, harmful to ourselves.

margin

You shouldn't have written in the margin since the book belongs to the library.

interval

It may be necessary to stop at intervals in the learning process and go back to the difficult points in the lessons.

bounce

A suburban Chicago car dealer for more than 30 years, Jack Phelan says the business has never been worse, but it will bounce back.

leap

The toy industry has witnessed great leaps in technology in recent years.

spring

As the old empires were broken up and new states were formed, new official tongues began to spring up at an increasing rate.

pattern

While U.S. diet is relatively identical, water supplies vary. The differences result from weather patterns.