Pati (Sanskrit: पति,) is a title meaning "master" or "lord". The word is in common usage in the Indian subcontinent today. Etymologically, the word derives from the Indo-European language family and finds references in various classical Indo-Iranian languages, including Sanskrit, Old Persian language and Avestan. In modern-day Hindustani and other Indo-Aryan languages, pati and patni have taken on the meanings of husband and wife respectively when used as standalone words. The feminine equivalent in Indo-Aryan languages is patni (literally, "mistress" or "lady"). The term pati is frequently used as a suffix, e.g. lakhpati (meaning, master of a lakh rupees).
The term pati is believed to originate from the Proto-Indo-European language. Older Persian languages, such as Avestan, use the term pati or paiti as a title extensively, e.g. dmana-paiti (master of the house, similar to Sanskrit dam-pati).
In Sanskrit, it is 'pat-' when uncompounded and meaning"husband" instrumental case p/atyā-; dative case p/atye-; genitive case ablative p/atyur-; locative case p/atyau-; But when meaning"lord, master", and in fine compositi or 'at the end of a compound' regularly inflected with exceptions;) a master, owner, possessor, lord, ruler, sovereign etc. For example, in the Vedas, we come across words such as Brhas –pati, Praja – pati, Vachas –pati, Pasu – pati, Apam –pati, Bhu pati, Tridasa – pati and Nr - pati. Here the 'pati’' is suffix translated as “Lord of …………..”
In several Indo-European languages, cognate terms exist in varying forms (often as a suffix), for instance in the English word "despot" from the Greek δεσ-πότης, meaning "master, despot, lord, owner." In Latin, the term changed meaning from master to able, and is "an example of a substantive coming to be used as an adjective," resulting in English words such as potent, potential and potentate. In Lithuanian, pats as a standalone word came to mean husband, himself (patis in Old Lithuanian), as did pati in Hindi/Hindustani.