How can I specify pyridine as a substituent? You know how when you carry out a reaction with many compounds, when drawing the reactions you just draw a line at a right angle to the bond with a 'R' at the end (see image)?



Then you can specify what group R is in a table (eg: $\ce{OMe}$). However, if instead of adding a substituent to a benzene ring, you have pyridine? How can you specify it?
The issue, I think, is to specify how the pyridine is connected. This means you have to identify which carbon on the pyridine ring is connected. This picture shows the numbering:



So, using your example the structure and names of the various possibilities would be (using connections on the 3-position of the benzonitrile ring as an example):



I'm sure you can generalise from this example.