"You have no business running around on a frontier world all alone."

The place was settled at least a thousand years ago, and yet it still has the feel of a frontier world.

He proved himself early on to be a political master of this roiling frontier world.

She had no military experience, but she'd lived on frontier worlds most of her life.

He could become a farmer on some frontier world.

The main house and surrounding village was the closest thing to a capital center this frontier world had to offer.

"Either of you ever been down on a frontier world before?"

"I thought it was a frontier world with nothing but savages."

The others would have acted like our scientists did on that frontier world.

We have to go to this awful frontier world for a year, maybe two, because my husband is stationed there.