The correct spelling of the word is "Clematis" /ˈklɛmətɪs/. The word is derived from the Greek word "klema," which means "vine branch." The correct spelling can be remembered by paying attention to the consonant cluster "tis" which is pronounced as /tɪs/. The erroneous spelling "Clematice" is a common mistake due to confusion over the correct pronunciation of the word. It is important to use correct spelling to communicate effectively and to avoid confusion.