Heard spelling

korymb

Spelled corymb. a hard c

The Greek word begins with a kappa, so why c?

Because it reached English through Latin, and Latin wrote kappa as c.

Korymbos became corymbus and then corymb. The k is historically correct and orthographically dead. Almost every Greek k in English went through the same conversion, which is why the language has cardiac, chorus, cycle and crisis rather than kardiac, khorus, kykle and krisis.

Say

KORR-im, with the b usually silent

Letters

C-O-R-Y-M-B