The term 'YOGA SURFACE' is a combination of two words, 'YOGA' and 'SURFACE'. YOGA is an ancient practice originating in India that combines physical postures, breathing exercises, and meditation. A SURFACE is a flat or curved area that forms the outer boundary of an object. Therefore, the term 'YOGA SURFACE' refers to a flat or curved area used for practicing YOGA. The crossword solution for this term is MAT, which stands for 'MATS', which are commonly used as a SURFACE for practicing YOGA.