кай

I (pron.) when; 
~ боз?, аз ~ боз? since when?; 
as long ago?; 
that ?; 
то ~?, то ба ~? till what times?; 
ким-~, ~ҳо боз very long ago
II (n.) hist. kay (title of old iranian king)

қай

(n.) vomiting, retching; 
~ кардан to be sick, to vomit