Conjecture
Speculation, Guess
noun, verbal noun, の adjective
すいそく
推定 (すいてい) Estimation, Estimate
推測 (すいそく) Conjecture, Speculation, Guess
憶測 (おくそく) Guess, Speculation
予測 (よそく) Prediction, Estimation, Forecast
すい starts with S just like Speculation.