Template:M summ IETA Period Traded Allowance
You might, and the ISDA EU Emissions Annex did, skip the redundant definition and just call this an “Allowance”. But anyway. An “Allowance” is the generic term for any legitmate emissions allowance under the EU ETS; a “Period Traded Allowance” is one from the compliance period that is specified in the Confirmation relating to this Transaction.