Adjective.....

Proper Use of the LEGO Trademark on a Web Site
If the LEGO trademark is used at all, it should always be used as an adjective, not as a noun. For example, say "MODELS BUILT OF LEGO BRICKS". Never say "MODELS BUILT OF LEGOs".Also, the trademark should appear in the same typeface as the surrounding text and should not be isolated or set apart from the surrounding text. In other words, the trademarks should not be emphasized or highlighted. Finally, the LEGO trademark should always appear with a ® symbol each time it is used.

Source : http://aboutus.lego.com/en-us/legal-notice/fair-play/