This is the 38th most frequent Hungarian word.
egy
"One" or "a/an."
Here, 'egy' functions as the indefinite article in Hungarian, equivalent to 'a' or 'an' in English, indicating that 'ház' (house) is indefinite.
Van egy ház a domb tetején.
There is a house on the top of the hill.
In this sentence, 'egy' is used for emphasis, akin to saying 'a really great idea' in English, stressing the value of the suggestion.
Ez egy remek ötlet.
This is a great idea.
The word 'egy' here implies 'a certain' or 'one', introducing that not just any friend but a specific one was the visitor yesterday.