thia-
I.combining form 
or thi-
Etymology: International Scientific Vocabulary, from thi- + -a- 
 : containing sulfur in place of carbon or regarded as in place of carbon usually in place of the methylene group −CH2− 
< thiacyclohexane >
< thiadiazole >
< thiazole >
— compare aza-, oxa-
II.combining form 
 : thi- 
< thiachroman >
I.
or thi-
< thiacyclohexane >
< thiadiazole >
< thiazole >
— compare aza-, oxa-
II.
< thiachroman >
thia-
Prefix
- Used to form the names of chemical compounds containing sulfur, especially such compound in which a sulfur atom replaces an oxygen atom in an analogous compound