Matching Pairs Concepts to Definitions MatchOnline version Match each concept with its brief definition. by Aida Fathi 1 Photosynthesis 2 Matrix (math) 3 Gravity 4 Atom 5 Democracy 6 Water cycle 7 Ecosystem 8 Cell nucleus People govern through voting. Continuous movement of water. A community of living and nonliving parts. Rectangular grid of numbers. Smallest unit of matter. Plants make glucose using light. Force pulling objects toward Earth. Control center of the cell.