Complex sentence: His work in general relativity included the theory of gravitational collapse; he coined the term "black hole" in 1967 during a talk at the NASA Goddard Institute of Space Studies (GISS).
Split into simpler sentences: His work in general relativity included the theory of gravitational collapse. The term "black hole" was coined in 1967 during a talk he gave at the NASA Goddard Institute of Space Studies (GISS).