which is better?

I have looked and I can't find an answer here. Which is better for
a domain,,.....adding an s to your keyword or a whole word at end?
Example.....dogtrainingbookss...or dogtrainingbooksonjline????
Any insight would be appreciated....
Thanks

I'm assuming your typo of the word "online" is unintentional. Best thing to do is use the google keywords tool and make your domain match the keywords you target as much as possible. No one is going to type the extra s in bookss unless it's an accident, so either use hyphens between words or come up with great keywords only for the domain name.

You are right, it was a typo.
My keys are sticking on my computer.
Hot here in Sacramento...
I appreciate your fast reply......
Thanks much..and have a great weekend.