Kimariji is a term used for Hyakunin Isshu play cards (a game based on a famous poetry anthology, One Hundred Poems by One Hundred Poets); when a card of the first half of a poem is read out, players compete to take a matching card of the last half, and Kimariji means the first several letters of poems with which players can be sure which card to take.
決まり字（きまりじ）とは、百人一首で札の取り合いをする際に、そこまで読まれればその札だと確定できるという部分のことを指す。