Ceacht 9:
ag	at	prep	
ag an doras	at the door 	[prep]+[art]+[n m1]	
ag an tine 	at the fire	[prep]+[art]+[n f4 ]	
ag an teach	at the house	[prep]+[art]+[n m]	
ag an siopa	at the shop	[prep]+[art]+[n m4]	
ag an scoil	at the school	[prep]+[art]+[n f2]	
ag an séipéal	at the chapel	[prep]+[art]+[n m1]	
an garda	the guard	[art]+[n m4]	
an múinteoir	the teacher	[art]+[n m3]	
féin	self	pron	
ach	but, except	conj	
ach tú féin	except yourself	[conj] + [pron] + [pron]	
sise	she (emphatic)	pron { Emphasized form of 'sí' }	
eile	other	determiner	

[ag] + [an]:  There are rules which govern the use of some prepositions (for example ag) when used with the singular definite article an.  In Standard Irish, ag + an causes eclipsis to nouns beginning with B, C, F, G or P, regardless of the gender of the noun.

This lesson only uses nouns beginning with D (doras), S (siopa) and T (tine) and the rule doesn't apply.