A menagerie of terms for legal specialists in-house

I am aware of at least six terms for legal specialties within law departments (See my post of May 5, 2008: 30 references to specialists.).

(1) Some general counsel refer to core competencies (See my posts of June 4, 2007: nine references to core competencies; and Aug. 5, 2007: clash between core competency and full service.). They mean, I think, the legal knowledge and skills most essential to the company’s profitability.
(2) Others use the phrase Centers of Excellence for clusters of very experienced lawyers (See my post of Feb. 4, 2008: Centers of Excellence.).
(3) Likewise “shared services” describes specialists who provide legal counsel to business unit lawyers (See my posts of Feb. 4, 2008: five references to shared services.
(4) Another expression is areas of expertise (See my post of Nov. 6, 2007: “areas of expertise” at Freddie Mac rather than functional lines or business units.).
(5) Others refer to practice groups (See my post of May 14, 2006: practice groups, as distinct from business unit groups and specialists.).
(6) “Subject matter experts” constitute another term for specialists (See my post of March 17, 2006: online list of SME’s.).

The shades of meanings between these variations elude me. The essence, however is that certain lawyers in corporations focus their work in narrower fields of law than do other lawyers.