What constitutes a paragraph?

Question

What constitutes a paragraph?

Answer 1

One thought and the expansion on that thought.

Answer 2

About 5 related, well-formed sentences.

Answer 3

The expression of a thought.  If you change thoughts, you change paragraphs.  But you can also split a paragraph in two, if it gets too long.  You want an intro sentence and a conclusion to open and close a thought, and then fill in the middle with your thoughts.  Intro/Conclusions will come to you; at first they're a little generic, but the more you write and read, you'll be able to see how others do it.

There really isn't a hard-set rule. Paragraphs in journalism tend to be pretty short, whereas in other forums they're much longer.  You basically want to break up your ideas so they don't become muddled in a big block of words.