Here's an aide-memoire re correct definitions re residential lettings and the Acts which create the varying types.
RENT ACT 1977
s.1: Protected Tenancy= letting of house etc. as separate dwelling.
s.2: Statutory Tenancy= what arises as a statutory continuation after Protected expires. NB: not same tenancy (unlike HA 1988 periodic continuation).
s.18: Regulated Tenancy= collective name for Protected or Statutory
s.18A: Controlled Tenancy= various pre-1980 tenancies converted into Regulated.
s.19: Restricted Contract (previously called "Part VI Contract")= letting where rent includes payment for furniture or services.
HOUSING ACT 1980
s.52: Protected Shorthold= letting (one yr to five yrs only), similar to HA 1988's original AST, ie preceded by warning Notice from L and with no security after fixed term expiry.
HOUSING ACT 1985
s.79: Secure Tenancy= public-sector letting of house etc. as separate dwelling when L condition [s.80] and T condition [s.81] are both satisfied.
HOUSING ACT 1988
s.1: Assured Tenancy=letting within 1988 Act, with effect from 15 January 1989.
s.19A: Assured Shorthold Tenancy=ditto preceded by s.20 Notice. These pre-date 1 March 1997.
s.20: Assured Shorthold Tenancy= ditto, but no need for preceding Notice. These post-date 28 February 1997.
Other 1988 Act lettings (ie not ASTs) are loosely described as Standard Assured Tenancies.
Hence one is best advised to use not the definition (in case it's wrong) but rather the name of the Act that governs the letting.