1The disputed frontier between the two nations has been a source of tension for decades.
2Space exploration represents the final frontier of human discovery, pushing the boundaries of what we thought was possible.
3The field of artificial intelligence is a rapidly evolving frontier, with new breakthroughs and innovations emerging every year.
4The company is at the frontier of sustainable energy, developing new technologies to reduce our reliance on fossil fuels.
5The concept of a 'digital frontier' has been used to describe the uncharted territory of the internet, where new social and cultural norms are being established.