A gap between a person's desire for social relationships and his/her actual social ties. Loneliness, which is a person's perceived social situation, is distinguished from social isolation, which refers to the objective number of social connections the individual has. A feeling of loneliness usually motivates to action (or prevents action), similar to the manner in which hunger and thirst are an internal clue that triggers action aimed at preventing harm to oneself – in this case, avoiding social interactions.
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