Member
Not every charity has members. Trusts do not; foundation-model CIOs have a membership that is the same people as the trustees; association-model CIOs and companies limited by guarantee have a wider membership that elects the board.
The liability position differs by structure, and the two incorporated forms are routinely reported as identical when they are not. Charities Act 2011 s.205(3)(b) permits a CIO constitution to cap member liability at a fixed maximum. The Scottish equivalent, CTI(S)A 2005 s.49(4), provides that SCIO members have no liability at all — it is not a constitutional choice.
Check which model your governing document uses before assuming who votes on what: see members and general meetings.