What's the "een" in Halloween?
chiasma chi·as·ma (kī-āz'mə) or chi·asm (kī'āz'əm)
n. pl. or chi·as·mas, chi·as·ma·ta (-mə-tə), chi·as·ms
A crossing or intersection of two tracts, as of nerves or ligaments.
The point of contact between paired chromatids during meiosis, resulting in a cross-shaped configuration and representing the cytological manifestation of crossing over.