Bydd and bydda are future tense forms. The correct suffixes for these are:
| Positive | Negative |
| Bydda i (I) | Fydda i ddim |
| Byddi di (You) | Fyddi di ddim |
| Bydd e/o (He) | Fydd e/o ddim |
| Bydd hi (She) | Fydd hi ddim |
| Byddwn ni (We) | Fyddwn ni ddim |
| Byddwch chi (You) | Fyddwch chi ddim |
| Byddan nhw (They) | Fyddan nhw ddim |
When using negative forms of the future tense bod, the b takes a soft mutation and is replaced with a f and ddim is also added. The positive forms should never be used with ddim.