A ta'anit or taynis (Biblical Hebrew תַּעֲנִית taʿaniṯ or צוֹם ṣom) is a fast in Judaism in which one abstains from all food and drink, including water.
There are two Jewish full fast days: The two full fast days carry four restrictions in addition to eating and drinking – one may not wash one's body, wear leather shoes, use colognes, oils or perfumes, or have sexual relations.
[7] Minor fasts are observed from dawn to nightfall, without additional restrictions.
"[13][14] Nowadays, the Jewish people are accustomed to observing these fasts, making them obligatory.
From the Gemara there is a prohibition against eating before Shacharit, the morning prayers, except for those who are ill or unable to concentrate.