In this Chapter—
“certified”, in relation to a section 8(4) certificate, means of a description certified by the certificate as a description of material the examination of which the Secretary of State considers necessary;
“external communication” means a communication sent or received outside the British Islands;
“intercepted material”, in relation to an interception warrant, means the contents of any communications intercepted by an interception to which the warrant relates;
“the interception subject”, in relation to an interception warrant, means the person about whose communications information is sought by the interception to which the warrant relates;
“international mutual assistance agreement” means an international agreement designated for the purposes of section 1(4);
“related communications data”, in relation to a communication intercepted in the course of its transmission by means of a postal service or telecommunication system, means so much of any communications data (within the meaning of Chapter II of this Part) as—
is obtained by, or in connection with, the interception; and
relates to the communication or to the sender or recipient, or intended recipient, of the communication;
“section 8(4) certificate” means any certificate issued for the purposes of section 8(4).