The practices that are prohibited on yom tov, as on Shabbat, whether because they are optional for that time or mitzvot - beginning with yibum and halitzah, as well as sanctifying produce and other to the Beit HaMikdash. Because what if one comes to write? What if it appears to much to be business practices? Also, how terumot and maaserot "fix" produce, and how this can become an issue on yom tov (challah, cough cough). Plus: A new mishnah, on the travel limitations on Shabbat or yom tov, and whose limitations determine how far one's property can be moved. And - another mention (of course!) of "bereirah" - retroactive designation, this time by Amoraim.