Kaasluse
Kaasluse is an Estonian abstract noun meaning the state or quality of being a kaaslane (a companion or associate). The word is formed from kaaslane with the abstract-noun suffix -use, and is used to refer to companionship, fellowship, partnership, or collaborative relationships. In sociological, literary, and philosophical contexts, kaasluse can describe the nature of social ties, the experience of being part of a group, or the act of cooperating on a project.
Kaasluse is closely related to kaaslane (companion) and to related terms describing social ties, such as sõprus
The term is primarily used in Estonian-language discourse and is understood by speakers across standard registers.