* Scottish Gaelic: You could use phrases like `grèin na grèine` (sun of the sun) or `solas na grèine` (light of the sun) for a more poetic feeling, emphasizing the light. `Grian` (sun) on its own might work in casual conversation, though it's not literally "sunshine."
* Irish Gaelic: Similar to Scottish Gaelic, you'd likely use descriptive phrases. `Grian na gréine` (sun of the sun) or `soilse na gréine` (light of the sun) would be analogous to the Scottish Gaelic options. `Grian` (sun) alone could be used informally.
Therefore, there's no single word equivalent. The best choice depends on the context.