/
ˈθiːsɪs/
n.
 (pl. theses  
/-siːz/
)
   - a statement or theory that is put forward as a premise to be maintained or proved. 
▸(in Hegelian philosophy) a proposition forming the first stage in the process of dialectical reasoning. Compare with antithesis, synthesis.
 - a long essay or dissertation involving personal research, written as part of a university degree.
 -  
/also ˈθɛsɪs/
 Prosody  an unstressed syllable or part of a metrical foot in Greek or Latin verse. Often contrasted with arsis.
 
Etymology
ME: via late L. from Gk, lit. ‘placing, a proposition’, from the root of tithenai ‘to place’.