In Irish, the traditional way to say “goodnight” is “Oíche mhaith” (pronounced “ee-ha wah”). This phrase literally translates to “good night” and is a common way to bid farewell or say goodnight to someone in Ireland.

In addition to “Oíche mhaith,” there are other ways to say goodnight in Irish, depending on the regional dialect and context. For example, in the Munster dialect, it is common to say “Codladh sámh” (pronounced “kull-uh sawv”), which means “peaceful sleep.” In the Connacht dialect, one might say “Oíche chiúin” (pronounced “ee-ha hyoon”), which translates to “quiet night.”
It is also worth noting that Irish is not the only language spoken in Ireland, and there are other languages and dialects that may be used to say goodnight. For example, in Ulster Scots, one might say “Guid nychburris” (pronounced “gid nick-burrs”), which is a variation on the Scottish “good night” greeting.
The use of Irish language greetings and phrases has been promoted in recent years as a way to preserve and celebrate Irish culture and heritage. In addition to “Oíche mhaith,” there are other Irish language phrases and sayings that are commonly used in everyday life, such as “Sláinte” (pronounced “slawn-cha”), which means “health,” and is often used as a toast when drinking with friends.
In conclusion, the traditional way to say “goodnight” in Irish is “Oíche mhaith.” However, there are other regional dialects and languages spoken in Ireland that may have different ways of saying goodnight. The use of Irish language phrases and greetings is an important way to celebrate and preserve Irish culture and heritage.