Please would someone explain to me what a chord is in railway terminology? TIA
A chord is a short section of track connecting two railway lines. Usually otherwise unconnected, but there are exceptions
An example, local to me, the slightly confusingly named 'Bacon Factory Curve' chord which connects the Great Eastern Mainline and East Suffolk
That allows trains coming from up north on the GEML or even ECML to access the docks at Felixstowe without having to enter Ipswich S.S or Ipswich Station and run their locomotive around.
It's almost exclusively for freight, the only passenger working I know of using it was the The 4 Triangles Railtour on the 9th of May 2015