Bíonn ainmfhocal nó forainm mar ainmní na habairte más é an t‑ainmfhocal nó an forainm sin atá ag déanamh an ghnímh a bhfuiltear ag tagairt dó san abairt.
A noun or a pronoun is the subject of a sentence if it is that noun or pronoun that is performing the action which is being referred to in the sentence.
Sampla: (Example)
Rinne Séamas a lán oibre ar maidin agus d’imigh sé go Sligeach tráthnóna.
Séamas did a lot of work in the morning and he went to Sligo in the afternoon.