Nexus
A connection or link.
A causal connection.
A connected series.
'Nexus' comes from the Latin 'nectere' meaning 'to bind.' The same Latin root gave rise to 'connect' and 'annex.' 'Nexus' achieved some currency as the title of a book by Henry Miller (1891-1980).
Following 'Sexus' (1949) and 'Plexus' (1953), 'Nexus' (1960) completed Miller's 'Rosy Crucifixion Trilogy.'