When i targeted keyword in singular and plural. What should i choose? Should i base my website around plural "wood tables" so for example people searching for "wood table" will also get to my site? Maybe i should create 2 sites woodtable.com and woodtables.com so i will get traffic searching for "wood table" and "wood tables"? In short should i create 2 websites (singular+plural) or one website with plural will be enough and will catch traffic searching for singular?
I would do one website - whichever has more search volume - and optimize for both singular and plural.
Use the adwords traffic estimates to get an idea of what is being searched for the most. But, ColeenB is correct that you will ultimately want to target both. The onsite optimization for plural/singular is pretty straightforward. Getting proper anchor text in links can be a bit more problematic, depending on our approach.
I go for plural one. because it takes both. singular as well as plural. you can achieve good ranking for both terms if you optimize well.
Google and probably all others search engines use linguistic analysis to get to the root form of a word, this procedure being called stemming. So, mainly, the root form of word is used for data mining, but most likely, an EXACT MATCH gives a bonus in search.
If your website is very informative, it won't matter whether it's plural or singular. Google will put you on top for broad match search. It only makes a difference if the user uses phrase or exact match.
Rather than quote all the people who gave incorrect advice, I'll just say now for the record that even with the linguistics and word stemming, it STILL matters whether you use the singular or plural version of a keyword. One can bring more search traffic than the other, depending on how many people search using that keyword. While Google has gotten better, it still tries to think like a searcher (human user), so if you want to think like them, think like the people who will be using your Web site.
Dan is correct, the singular and plural generate different results. Just do a Google search for wood table vs wood tables and you'll notice not only a different top ten list, but a different number of total returned results as well. This is true for any keyword.