Also cteno-. A prefix meaning comb or comb-like. From the Greek Kten- or Kteno-, meaning 'shaped like a comb', 'having narrow parallel projections'. Pronounced 'ten-' or 'teen-'.
Used a lot in biology, for example:
ctenidium
ctenii
ctenocyst
ctenoid
And names for taxanomic categories:
ctenacanthus
ctenacodon
Ctenizidae
Ctenoidei
Ctenophora
Ctenostomata