frontier
Pronunciation
Noun
B1 Intermediate
Quick answer
The border between two countries, or the outer limit of what is known or has been achieved.
Synonyms and antonyms
Usage notes
"Frontier" often appears in the figurative phrase "the frontiers of science," referring to the edge of current knowledge.
Test yourself
Which word fits the gap? "Researchers are pushing the _____ of what we know about the deep ocean."
Answer: frontier
In your own words, what does "frontier" mean?
The border between two countries, or the outer limit of what is known or has been achieved.
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