Abstract: A composition that includes Compound (a) and Compound (b). Compound (a) is represented by formula (1): where: Ar represents an aromatic ring; m represents an integer of 2 to 8; n represents an integer of 0 to 6, provided that m+n is the number of carbon atoms constituting the aromatic ring, or less; and R1 each independently represents an alkylthio group, a halogen group, a hydroxy group, a dialkylthiocarbamoyl group, or a dialkylcarbamoylthio group. Compound (b) is represented by formula (2): where p represents an integer of 0 to 4, and q represents an integer of 0 to 2.

Abstract: A composition containing: a compound (a) represented by Formula (1): wherein Ar represents an aromatic ring, m represents an integer of 2 to 8, n represents an integer of 0 to 6, provided that m+n is equal to or less than a number of carbon atoms that constitute the aromatic ring, and R1 each independently represents an alkylthio group, an epoxyalkylthio group, a thiol group, a halogen group, a hydroxy group, a dialkylthiocarbamoyl group, or a dialkylcarbamoylthio group; and 1,2,3,5,6-pentathiepane (b).

Abstract: A composition containing: a compound (a) represented by Formula (1): wherein Ar represents an aromatic ring, m represents an integer of 2 to 8, n represents an integer of 0 to 6, provided that m+n is equal to or less than a number of carbon atoms that constitute the aromatic ring, and R1 each independently represents an alkylthio group, an epoxyalkylthio group, a thiol group, a halogen group, a hydroxy group, a dialkylthiocarbamoyl group, or a dialkylcarbamoylthio group; and a polythiol (b).

Abstract: A composition for an optical material contains (a) an episulfide compound, (b) a polymerization catalyst, and (c) an ester compound having a halogen at the ? position. The (c) ester compound having a halogen at the a position is preferably at least one compound selected from the group consisting of dimethyl chloromalonate, diethyl chloromalonate, dimethyl bromomalonate, and diethyl bromomalonate.