Question

s English sass, center. Spanish sosos. Outside of northern Spain it can also be spelled z (zapato) or c (cero, cielo) (in northern Spain the letters z and c have a different sound: [θ]). This sound is pre-dorso-alveolar. In northern Spain the s is typically apico-alveolar: [s̺]

Accepted Answer

Voiceless Alveolar Fricative (Sibilant) http://en.wikipedia.org/wiki/Voiceless_alveolar_sibilant

Symbol	s
Name	Voiceless Alveolar Fricative (Sibilant)
Notes	English sass, center. Spanish sosos. Outside of northern Spain it can also be spelled z (zapato) or c (cero, cielo) (in northern Spain the letters z and c have a different sound: [θ]). This sound is pre-dorso-alveolar. In northern Spain the s is typically apico-alveolar: [s̺]
Ref	http://en.wikipedia.org/wiki/Voiceless_alveolar_sibilant

S C Northern Spain Z Alveolar O Voiceless