開発 (kaihatsu) is to develop something through exploitation of resources, for example, when you develop a new product. R&D is 研究と開発 (kenkyu to kaihatsu). A software developer is 開発者 (kaihatsusha). 発展 (hatten) is development through growth or expansion. A developing country is 発展途上国 (hattenntojokoku).