This is an old revision of the document!
The short form of the Loneliness Scale measures subjective social isolation, which is defined as a situation experienced by the participant as one where there is an unpleasant or inadmissible lack of (quality of) certain relationships. It includes situations where the number of existing relationships is smaller than desirable or acceptable, as well as situations where the intimacy wished for has not been realized 1).
https://home.fsw.vu.nl/tg.van.tilburg/manual_loneliness_scale_1999.html