The Raychaudhuri equation is central to the understanding of gravitational attraction in astrophysics and cosmology, and in
particular underlies the famous singularity theorems of general relativity theory. This paper reviews the derivation of the
equation, and its significance in cosmology.
Keywords General relativity - singularity - cosmology
PACS Nos 04.20.Dw - 47.75.+f - 95.30.Sf - 98.80.-k - 98.80.Jk