English: transitional waters (estuary) 
Welsh: dyfroedd aberol
Subject: Amgylchedd
English definition: Bodies of surface water in the vicinity of river mouths which are partly saline in character as a result of their proximity to coastal waters but are substantially influenced by freshwater.
Welsh context: Gall y term ‘transitional waters’ hefyd olygu morlynnoedd a ffiordau. Os oes angen defnyddio term nad yw mor benodol â ‘dyfroedd aberol’, gellid defnyddio term fel ‘dyfroedd lled groyw’.