"Detached house"

Translation: Tŷ ar wahân

[HerrArbo]

What would the difference in pronunciation be between "tŷ" and "ty"?

[ibisc]

The acen grom/to bach/circumflex over the y in tŷ indicates that it is a long vowel with the English /ee/ sound. Without that, ty might be pronounced as a short vowel with the obscure /uh/ sound, as in the Welsh dy, fy, yn.