Ceacht 10
a 	her / their	{ [poss pron] / [a.] }	
a bricfeasta	her breakfast	[pron] + [n m4 ]	
ag a béile 	at her meal 	[prep]+[pron]+[n m4]	
ag a bricfeasta 	at her breakfast 	[prep]+[pron]+[n m4]	
ag a lón	at her lunch	[prep]+[pron]+[n m1]	
ag a dinnéar	at her dinner	[prep]+[pron]+[n m1]	
ag a tae	at her tea	[prep]+[pron]+[n m4]	
ag a suipéar	at her supper	[prep]+[pron]+[n m1]	
an leanbh	the child	[art]+[n m1]	
na leanaí	the children	[art]+[pl n m1]	
a lón	their lunch	[pron]+[n m1]	
go léir	all	prep phrase	
fós	yet	adv	

The personal pronoun a (her or its) prefixes the letter h to nouns beginning with a vowel.
Thus far in the course, we've only used 2 nouns beginning with a vowel ( -> Lesson 2), Aimsir and Oíche (weather and night). If, for example, we wanted to say "her night" we would use "a hoíche".

a (their):  The personal pronoun a (their) causes eclipsis to nouns beginning with a consonant or prefixes the letter n- to nouns beginning with a vowel.  This lesson uses the noun lón (lunch) but the consonant L is not subject to eclipsis. If, for example, we wanted to say "their breakfast" we would use "a mbricfeasta" 

na (the): Irish, has a different definite article for plural nouns, na.
an leanbh - the child,		na leanaí - the children.

If the noun begins with a vowel, prefix h is added to the noun.

Plural nouns:  There are a number of ways in which Irish plural nouns are formed, but it is perhaps best, at this stage of our studies, to simply learn the plural form together with the singular, also with the plural form of the definite article “na" (see above).  For some of the nouns we've covered so far in this course:

an lá 		- the day 		> na laethanta 		- the days,
an oíche 	- the night	 	> na hoícheanta 	- the nights,
an mhaidin 	- the morning 		> na maidineacha 	- the mornings,
an fear 		- the man 		> na fir 		- the men,
an bhean 	- the woman 		> na mná 		- the women,
an buachaill 	- the boy 		> na buachaillí 	- the boys,
an cailín 	- the girl 		> na cailíní 		- the girls,
an garda 	- the guard 		> na gardaí 		- the guards,
an múinteoir 	- the teacher 		> na múinteoirí 	- the teachers,
an leanbh 	- the child 		> na leanaí 		- the children.

Many of the frequently used nouns are irregular in the plural, 
for example fir (men) and mná (women). 
You will also notice that maidin (morning) is subject to lenition after the singular definite article ("an") because it is a feminine noun, but that rule does not apply after the plural definite article ("na").