The article studies the economic essence, signs, and characteristics of the endowment. Based on the generalization of the views of domestic scientists and the interpretations available in the normative and legal documents, the lack of a unified approach to determining the essence and key characteristics of the endowment is revealed. The article identifies the characteristic features of endowment: formation of endowment for the needs of non-profit organizations; sources of endowment replenishment, including financial, tangible and intangible assets, and income from their use; permanent nature of endowment with mandatory subsequent placement in market assets; mandatory management of endowment by own means or by transferring permanent capital to trust management; clear instructions for the use of the endowment and the income received based on the statutory goals of the non-profit organization, as well as conditions and restrictions imposed by the donors on its use; the use of the received income to finance the activities of non-profit organizations and cover the administrative costs of managing the fund; the possibility for a non-profit organization to create, maintain, and manage several endowments; the establishment of special conditions for the creation of endowment and its capitalization. The article emphasizes a significant difference between endowment funds and various types of charitable aid, which is manifested in long-term use, since the donors’ funds are "oriented" to the long-term period and obtaining additional income from the investment of accumulated resources. The author offers a definition of endowment as a permanent capital that is formed at the expense of financial and material values voluntarily provided free of charge by external donors to a non-profit organization indefinitely or for a certain time, which is transferred to the management and used exclusively for financing the statutory activities of the organization in terms of passive income received from the investment of the basic capital in market assets. The relevance and prospects of spreading the idea of endowment formation in the activities of domestic non-profit organizations as an important factor in attracting additional resources and expanding the financial base for the implementation of future goals and projects are outlined. The article identifies a set of principles that form the theoretical basis of the functioning of endowment funds: social significance; the integrity of the gift; investment; transparency; intended purpose; constant growth of the "body" of the endowment; accountability and control; dependence of the effect on the volume. 

endowment, endowment fund, investments, financial donations