"Our relatives eat at the wedding."
Translation:Itheann ár ngaolta ag an bpósadh.
As in English, both terms are widely used in the vernacular for terms associated with the actual event (both languages have lost the distinction between the specific event and the associated celebration, for the most part):
comóradh diamaint pósta - "Diamond wedding anniversary"
bainis eaglaise "A church wedding" but you also have "some people prefer a church wedding" - is fearr le daoine áirithe pósadh san eaglais
fáinne pósta - "a wedding ring"
gúna pósta - "a wedding dress"
cáca bainise - "a wedding cake"
bainis bhán - "a white wedding"
lá do phósta, lá do bhainise - "your wedding day"
nuaphósta - "newlywed"
For terms associated with "marriage", such as "marriage guidance" or "married name", pósta is used.
Irish has thousands of words that aren't included in this course - you won't find the words for "hard drive" or "monitor" or "plug" or "cable" on the course, just to mention some of the things that you might have within arms length if you're using a computer to do Duolingo.
There are finite limits to the vocabulary that any course can teach, in any language. And many words have synonyms - the vocabulary of an introductory language course typically prefers to teach you three different words rather than three synonyms for a single word.
gaolta means "relatives". After plural possessive adjectives (our, your, their), you eclipse the noun - ngaolta. After singular possessive adjectives (my, your, his) you lenite - ghaolta. (The exception is "her" which doesn't eclipse or lenite).
The difference is most helpful for a, which can mean "his" (a ghaolta - "his relatives"), "her" (a gaolta - "her relatives") or "their" (a ngaolta).