Space is the final frontier for man to explore.
The soldiers headed for the frontier with caution.
The soldiers proceeded to the frontier with caution.
Many families left to make a new life on the frontier.
Many families went west to make a new life on the frontier.
The frontier between the two countries was temporarily closed.
The frontier has been closed due to rebel activity in the region.
Our car was searched by customs officials when we got to the frontier.
The border between the United States and Canada is the world’s longest frontier.
Find someone who has crossed an international frontier in the last six months.
Swaziland is surrounded by South Africa, except for a short frontier with Mozambique.
Brazil shares a frontier with all South American countries, except Ecuador and Chile.
The people on the fringes of society often must rely on charity to make ends meet.
Scientists working on cloning techniques are on the frontier of a new era for the human race.