示差 is read as しさ (shisa) and means differential.
しさ
shisa
さしかえひょうじ
obsoleting indication
しめす
to point out (finger, clock hand, needle, etc.)
しめし
revelation
じだん
settlement out of court
しめしあわせる
to arrange beforehand
しめしあわす
to conspire (with)
じげん
manifestation (of a celestial being)
しど
indication
しそうかせき
facies fossil
じし
index finger
じだんきん
settlement money
しせいしき
rational formula