Abstract
A review of theoretical and experimental results obtained for the triglycine selenate (TGSe) ferroelectric has been presented. It has been stressed that the critical character of paraelectric–ferroelectric phase transition in TGSe or that close to tricritical had been confirmed in many articles. However, in the paraelectric region the properties of TGSe can be characterized as being between the Landau critical point type of behaviour and that of the Landau tricritical point. Different examples of such a discrepancy have been cited. Some properties of TGSe have been discussed in relation to those of the structurally isomorphous triglycine sulphate ferroelectric. The theoretical models used for TGSe in the literature have been briefly discussed.