English: supplementary vote
Welsh: pleidlais atodol
Subject: Pwyllgorau
Welsh definition: The Supplementary Vote (SV) is a shortened version of the Alternative Vote (AV). Under SV, there are two columns on the ballot paper – one for voters to mark their first choice and one in which to mark a second choice. Voters mark one 'X' in each column, although voters are not required to make a second choice if they do not wish to. 
Plural: pleidleisiau atodol
Notes: Dyma’r system a ddefnyddir yn etholiadau’r Comisiynwyr Heddlu a Throseddu.