Tywydd, n. the weather
Tywyll, n. dusk, gloom: a. dark, obscure, dusky
Tywylliad, n. a darkening
Tywyllod, n. obscurity
Tywyllu, v. to darken, to obscure
Tywyllwch, n. darkneas
Tywyn, n. spread, ray; strand
Tywynedig, a. illumined
Tywynedigaeth, n. radiancy
Tywyniad, n. radiating, shining