Seeing an inkwell may make a listener immediately think of a pen because the two have often been encountered together. Such association can illustrate jāmiʿ khayālī: one representation evokes another, without their necessarily being linked by logical entailment.
هَذِهِ مِحْبَرَةٌ، وَهَذَا قَلَمٌ.
This is an inkwell, and this is a pen.
Shared educational experience supplies a plausible association. It would be a category error to classify every habitual mental sequence as a necessary rational relation.