Is this question a paragraph? Does it need 5 sentences to be a paragraph?
in my opinion, when standing on its own, it becomes a paragraph when it takes up multiple lines without using linebreaks (return/enter). however, i believe a 1-line paragraph could exist only when surrounded by other paragraphs, as long as some of those other paragraphs take up more than one line (without linebreaks). of course this all depends on the width of the page. i should also mention that if you make the page so narrow that there's only 1 word per line, that also doesn't count as a paragraph because it becomes a word list. but as long as at least one line is wide enough for 2 words, then it becomes a paragraph again