Three dimensions of loneliness

Intimate or emotional loneliness is the longing for a close confidant or intimate partner. Someone with whom you share a deep mutual bond of affection or trust.
Relational or social loneliness is the yearning for quality friendships and social companionship and support.
Collective loneliness is the hunger for a network or community of people who share your sense of purpose and interests.

These three dimensions reflect the high range of quality social connections that humans need in order to thrive. The lack of relationships in any of these dimensions can make us feel lonely which helps to explain why we may have a supportive marriage but still feel lonely for friends and community."

-- Together: The Healing Power of Human Connection in a Sometimes Lonely World by Dr. Vivek Murth