«فَيَقُولُونَ فِي الْمُطْلَقِ وَالنِّسْبِيِّ: تَفَرَّدَ بِهِ فُلَانٌ، أَوْ أَغْرَبَ بِهِ فُلَانٌ»
For either absolute or relative cases, critics may say that someone transmitted a report alone or with singularity.
The pronoun in bihi refers to the report under discussion. The expression signals isolation at a relevant point, but the exact point normally depends on the surrounding chain details.
Example: If a critic writes “N alone transmitted it from M,” that specifically identifies N's relationship to M. Additional investigation is needed to determine whether other independent original routes of the report exist.
A single lexical formula cannot replace reconstruction of the hadith's transmission history.