Historical Rules · 1 October 2010
Rule 304.3
Official source text from the 1 October 2010 Rules release
Instant subtypes are always a single word and are listed after a long dash: "Instant -- Arcane." Each word after the dash is a separate subtype. The set of instant subtypes is the same as the set of sorcery subtypes; these subtypes are called spell types. Instants may have multiple subtypes. See rule 204.3j for the complete list of spell types.