Standardised Welsh Place-names list
Notes
The hyphen is used when the Welsh definite article (y/yr) occurs before a final monosyllablic element; hyphens are used before and after the definite article in order to indicate the individual elements and aid pronunciation.
The standard reference book, A Gazetteer of Welsh Place-Names (University of Wales Press, 1967) uses tyn (without an apostrophe) for the contracted form of the Welsh noun tyddyn (homestead or smallholding).