"Dewi Lingo does not want milk."
Translation:Dyw Dewi Lingo ddim eisiau llaeth.
Dyw in this sentence just serves the same purpose as mae, except it's the negative form (since we have ddim/Dewi Lingo does not want milk!).
- Mae Dewi Lingo eisiau llaeth - Dewi Lingo wants milk
- Dyw Dewi Lingo ddim eisiau llaeth - Dewi Lingo doesn't want milk
Most of the conjugations of bod change when you use ddim, not just mae.
- (Ry)dw i eisiau llaeth - I want milk
- (Dy)dw i ddim eisiau llaeth - I don't want milk
The best way is probably learning to pronounce them right. The two sound very different if you say them correctly.
With wy you start with rounded lips and spread them to a smile: "oo-ee" (listen here).
With yw you start with spread smiling lips and round them: "oo-ee" (listen here).
If you want a quick way to remember the above words, you could think English "two" has a "w" in the middle as does Welsh dwy with the same meaning, whereas dyw doesn't. I dunno, that's off the top of my head. You can probably think of something better.