I would tend to think that you use the word 'column' if there are at least two of them, but not if there is just one body of text on a page. Here is what Wikipedia says:
In typography, a column is one or more vertical blocks of content positioned on a page, separated by margins and/or rules. Columns are most commonly used to break up large bodies of text that cannot fit in a single block of text on a page. http://en.wikipedia.org/wiki/Column_(typography)
I think that they call what you are looking for 'single block of text'.
Problem is, I'm writing a kind of catalogue, and I must consistently indicate whether the text is in "two columns" or in "single block of text" (as Thomas suggests to avoid the weird "one column")... Is there any other option?
Sorry I didn't give enough information in the previous thread.
Thanks Ewie, I see your second post only after I'd posted mine...