Is it still an EXACT domain if it has a hyphen? for example stainlesssteel.com and it becomes stainless-steel.com? Is it still a good domain? will search engines read it as stainless steel?
The search engines read hyphens as spaces, so yes. Register both versions if you can. Personally, I don't think it's a good idea to register the hyphenated version of a domain name if someone else has registered the non-hyphenated version, especially if it's an ecommerce site.
I agree completely. Even though SE's would read it as one single word, one should avoid using hyphens just to get the keyword... as you would always appear to be playing second fiddle to the site bearing the keyword without the hyphen! Regards, RightMan
but what if the domain name that is not hyphened is just parked and not being used as a site? so then the hyphenated domain will be ok?
Do you own it? If so, you can redirect from this domain to your hyphenated domain, to catch anyone who misses out the hyphen. The problem is, people might more easily remember the non-hyphenated version and use it by mistake, even though they're looking for your site. If a competitor owns the non-hyphenated domain, any promotions you do might send some business his way. The same could happen in reverse, of course, but I suspect to a lesser extent. If it were me, I would want to get both domains. If this isn't possible, I would prefer to have the non-hyphenated version.
It's still an exact word domain, but subjective in terms of what people would think of it in a domain name auction. Two word hyphenated domains are definitely considered an endangered species these days.
Hyphenated domains appear spammy. If you purchase a domain like that, try to get one with only a single hyphen. The more hyphens there are, the worse it is.