With recent NHS initiative to replace their clinical terminology, READ Version 3(or CTV3), with SNOMED CT (Systemized Nomenclature of Medicine Clinical Term), there may be a lot of questions raised about this terminology. I first knew about this terminology, in 2008, when I worked with NHS CFH as part of PhD projects. This might be the very early days for SNOMED CT in the UK. I wrote a chapter about SNOMED CT for my PhD thesis, but later on discarded it and never got it published. So I think it will be better if I publish it here, even though the content itself may be a little out of date by now. But I hope, it will be still beneficial for an introductory read. Bear in mind, some of the content may be relevant only to UK audiences.