Sadhu (साधु, IAST: (male), sādhvī or sādhvīne (female)), also spelled saddhu, is a religious ascetic, mendicant or any holy person in Hinduism, Buddhism, and Jainism who has renounced the worldly life. They are sometimes alternatively referred to as yogi, sannyasi or vairagi.
Sādhu means one who practises a 'sadhana' or keenly follows a path of spiritual discipline. Although the vast majority of sādhus are yogīs, not all yogīs are sādhus. A sādhu's life is solely dedicated to achieving mokṣa (liberation from the cycle of death and rebirth), the fourth and final aśrama (stage of life), through meditation and contemplation of Brahman. Sādhus often wear simple clothing, such as saffron-coloured clothing in Hinduism and white or nothing in Jainism, symbolising their sannyāsa (renunciation of worldly possessions). A female mendicant in Hinduism and Jainism is often called a sadhvi, or in some texts as aryika.
The term sadhu (Sanskrit: साधु) appears in Rigveda and Atharvaveda where it means "straight, right, leading straight to goal", according to Monier Monier-Williams. In the Brahmanas layer of Vedic literature, the term connotes someone who is "well disposed, kind, willing, effective or efficient, peaceful, secure, good, virtuous, honourable, righteous, noble" depending on the context. In the Hindu Epics, the term implies someone who is a "saint, sage, seer, holy man, virtuous, chaste, honest or right".
The Sanskrit terms sādhu ("good man") and sādhvī ("good woman") refer to renouncers who have chosen to live lives apart from or on the edges of society to focus on their own spiritual practices.
The words come from the root sādh, which means "reach one's goal", "make straight", or "gain power over". The same root is used in the word sādhanā, which means "spiritual practice". It literally means one who practises a ′′sadhana′′ or a path of spiritual discipline.
Unlike skilled workers and professionals, there is no certification for sadhus. So, it is very difficult to determine the exact number of sadhus.