Tower house at Ballagharahin in Co. Laois.
Transept - The portion of a church that forms the cross shape. The transepts of a church will be usually aligned N-S as opposed to the chancel and the nave which will have a E-W alignment.
Transom – A horizontal bar of wood or stone across a window and entrance.
Tracery – The ornamental work in the upper part of a window.
Tumuli – A round-barrow.
Turrett – A small circular tower that is used mainly for defence. They are often found at castle sites and rarely at ecclesiastical sites.