Sedra
The Torah portion to be read on a particular date.
Sefer Torah
Torah scroll.
Shacharit
The morning service.
Shamash
The ‘helper’ candle that lights the Chanukah candles. See ‘How to light Chanukah candles’ video here.
Shammas
The organiser of the service including aliyot, mitzvot, etc.
Shiur
A discussion or learning session, usually about a particular Torah reading.
Siddur
Shabbat and daily prayer book.
Simchah
Meaning ‘happiness’ or ‘joy’. Refers to a celebration.