Suppose I have a set $S$ and a natural number $m$. For $i\in S$, let $$X_i=\{a\subseteq S: \vert a\vert=m\mbox{ and }i\not\in a\}.$$ We then let the $m$-crown of $S$ be the indexed set $$\{X_i: i\in S\}.$$(with indexing set $S$ itself) $$(X_i)_{i\in S}.$$ For example, if $S=\{1,2,3,4\}$ and $m=2$ then e.g. $$X_2=\{\{1,3\}, \{1,4\}, \{3,4\}\},$$ and the whole $m$-crown of $S$ is $$\{$$$$($$ $$\{\{2,3\}, \{2,4\}, \{3,4\}\},$$$$X_1=\{\{2,3\}, \{2,4\}, \{3,4\}\},$$ $$\{\{1,3\}, \{1,4\}, \{3,4\}\},$$$$X_2=\{\{1,3\}, \{1,4\}, \{3,4\}\},$$ $$\{\{1,2\}, \{1,4\}, \{2,4\}\},$$$$X_3=\{\{1,2\}, \{1,4\}, \{2,4\}\},$$ $$\{\{1,2\}, \{1,3\}, \{2,3\}\}$$$$X_4=\{\{1,2\}, \{1,3\}, \{2,3\}\}$$ $$\}.$$$$).$$