The Frayer Model is an excellent model for defining concepts. It would work well alongside the Parts-Whole model which is great for defining things.
Article - Reading Strategies in the Science Classroom.
I am a teacher with over 25 years of experience in the classroom. I am currently working for the Institute of Professional Learning at the University of Waikato, working with schools and teachers to aid them in using digital technologies to support learning and in implementing future-oriented pedagogies.