Is é an tríú pearsa firinscneach den réamhfhocal (e.g. air, leis, aige) a úsáidtear leis na haidiachtaí taispeántacha, seachas an bunleagan den réamhfhocal (e.g. ar, le, ag).
The third person masculine form of the preposition (e.g. air, leis, aige) is used with the demonstrative adjectives, instead of the basic form of the preposition (e.g. ar, le, ag).
| Ceart Correct | Mícheart Incorrect |
| Anuas air sin ... As well as that ... | *Anuas ar sin ... |
| Chomh maith leis sin ... As well at that ... | *Chomh maith le sin ... |
| Tá tionchar aige sin ar an scéal ... That has an influence on the story ... | *Tá tionchar ag sin ar an scéal ... |
Seo thíos liosta de na leaganacha de na réamhfhocail a úsáidtear leis na haidiachtaí taispeántacha seo agus sin.
Below is a list of the versions of prepositions used with the demonstrative adjectives seo and sin.
| Bunleagan den réamhfhocal Basic form of the preposition | + seo nó sin + seo or sin | An tríú pearsa firinscneach den réamhfhocal The third person masculine form of the preposition |
| ag | + seo/sin | aige seo/sin at this/that |
| ar | + seo/sin | air seo/sin on this/that |
| as | + seo/sin | as seo/sin from this/that |
| chuig | + seo/sin | chuige seo/sin to this/that |
| de | + seo/sin | de seo/sin of this/that |
| do | + seo/sin | dó seo/sin to this/that |
| faoi | + seo/sin | faoi seo/sin under/about this/that |
| le | + seo/sin | leis seo/sin with this/that |
| ó | + seo/sin | uaidh seo/sin from this/that |
| roimh | + seo/sin | roimhe seo/sin before this/that |
| thar | + seo/sin | thairis seo/sin over/past this/that |
| trí | + seo/sin | tríd seo/sin through this/that |