"Is it big?"
Translation:Je to veliké?
The end "y" changed due to gender (like the answer other reads).
As to the "i" from what I vaguely remember, (it's been a very long time so I am here to brush up/re learn) "velikí" is/can be bigger/larger than just "velký". Sort of like the difference between big and huge. It is also used as "great", as in "Katherine the Great" = "Kateřina velika". As opposed to "velká Kateřina" which would be "big Katerina"
I also found this: http://www.wordbook.cz/index.php (need to scroll down on the page):
veliký - big
veliký - grand adjective
veliký - great
veliký - huge adjective
veliký - large
velký - big velký - bulk velký - bumper velký - grand adjective velký - great velký - high velký - large velký - magna</pre>
(not sure how I got the yellow in there, just ignore it:)