Using a few lines of an article is also not a copyright violation.
There is no real definition of "few lines" and so users must use their own judgement.
Publishing 10 lines from an article with 12 lines may be considered a copyright violation by many, but copying 15 lines from a 300 page book may not be seen a copyright violation by the same people.
As explained above, the substantiality of the copying is more important than the actual amount. For instance, copying a complete short poem is more substantial than copying a random paragraph of a novel;