reachability a term in graph theory where a point b is said to be reachable from a point a if there is a line between a and b; E. A. Wrigley ( 1973) uses r. in record linkage to refer to situations where two records are linked only indirectly through one or more intervening records (e.g., suppose a baptism record may be linked to a burial record through an intervening marriage even though the baptism and burial are not directly linked; here the burial is reachable from the baptism) (Cf. E. A. Wrigley, 1973)