That's a good question.
If you look in my new favorite dictionary, Merriam Webster you find:
Rhythm: the effect created by the elements in a play, movie, or novel that relate to the temporal development of the action
Cadence: a rhythmic sequence or flow of sounds in language the grand cadence of his poetry
The definitions aren't going to help much are they? This is one of the most interesting parts of being a word wrangler: really delving into the nuances of similar words.
I think the best way to talk about cadence is to read it or hear it.
This recent article in the WaPo has undeniable cadence: notice the short alternating paragraphs. It's almost like the call and response of the drill Sergeant calling cadence.
or for those Bill Murray fans in the audience
Clearly cadence is rhythmic, but not all rhythm is cadence.
Here's rhythm that isn't cadence
Bob Fosse is probably the closest to a cadence style in his choreography (oh god, what a great artist he was) but it's still not the call and response and repetition of true cadence.
Here's why this is important to think about: you always need rhythm, and sometimes the rhythm you need is cadence. Rhythm and cadence are conveyed with word choices. You can have flexible, flowy phrases and still have rhythm (think Faulkner) but cadence is going to use short sharp words. Think of the difference between marching and dancing.
Making these kinds of distinctions will help you choose just the right word which is a key element of compelling, interesting writing. Here are some examples to start you out:
1. Pale and wan
2. Amble and saunter
3. Rage and fume
4. author and writer
5. trump and win (oh yes, I did that one on purpose)
6. hurl and toss
7. invective and insult
8. gamble and risk
9. pay and remit
10. shark and agent (ok, ok, that's just a joke)
Yes you can go overboard on this, much like you can on commas and other forms of rebellious punctuation, but I'd rather fish you out of the lagoon, than not have you dive in.
11. Chastise and upbraid
12. snarl and growl
13. nefarious and underhanded
14. the devil and the deep blue sea (ok, that's also a joke)
Now, marching off to the office:
I don't know but I've been told
Query No's are really cold
Sound off! Sound off! Three, fourRequested fulls are sent with hope
Waiting time will make you mope
Sound off! Sound off! Three, four.Get "the call" and leap for joy
Ours is just to write and die!
Sound off! Sound off! Three, four