As we mentioned above (section 6), Tisha Be-Av is similar to Yom Kippur in two ways. It is an overnight fast (lasting 25 hours). Furthermore, we practice five forms of self-denial: eating and drinking, washing, applying cream, wearing leather shoes, and having marital relations (35:13 above).
However, since Tisha Be-Av is rabbinic, the sick are exempt from fasting. This is different from the biblical fast of Yom Kippur, when they are obligated to fast as long as their illness is not life-threatening (35:9-10).
There is one way in which Tisha Be-Av is actually more severe than Yom Kippur. On Tisha Be-Av we act as if we are in mourning (section 12 below). In contrast, while Yom Kippur is a fast, it is also a holiday (35:15 above).
