A graph or network is said to be fully connected if there is a link between every possible pair of nodes. The term is also often applied to adjacent layers in a neural network in tbis case it measnthat each node in one layer is connecetd to verey node in the next layer, but not that the nodes within a layer itself are connected.
Used on Chap. 6: pages 113, 117, 119, 120, 123; Chap. 7: page 146; Chap. 8: page 153; Chap. 9: page 189
Boltzmann Machine -- a fully connected network
Restricted Boltzmann Machine -- fully connected between layers, but not within layers