Articles in the English Language / Артикли в Английском языке

A: What does ... [the/a/an/--] word "frontier" mean? Doesn't it mean ... [a/an/--/the] line between two countries? I used ... [the/a/an/--] word in ... [a/an/--/the] conversation with ... [an/a/the/--] American friend yesterday, and he didn't understand what I was saying.
B: No, most Americans use ... [the/a/an/--] word "border" to express that idea. In fact, ... [--/a/an/the] "frontier" has ... [a/an/the/--] very different meaning for us in ... [the/a/an/--] U.S. Actually, ... [the/a/an/--] definition is related to ... [the/a/an/--] history of our country. When ... [the/a/an/--] English and other European settlers first came to ... [--/a/an/the] North America, they built towns and cities on ... [the/a/an/--] East Coast. As more colonists came to ... [the/a/an/--] new world, towns were built further west. Colonists called ... [the/a/an/--] unexplored wilderness beyond ... [the/a/an/--] towns and cities ... [the/a/an/--] "frontier".
A: Oh, that's why Americans call space ... [the/a/an/--] "last frontier". It means that space is ... [the/a/an/--] last unexplored place. I've heard ... [the/a/an/--] phrase several times, but I never understood it before. Wow, learning ... [--/a/an/the] vocabulary in ... [a/an/the/--] foreign language is really hard!

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