In Irish, as indeed for other languages, it is advised to break words at a “natural” point when a line of text reaches the right hand side of the page, by using a hyphen. Usually, the person writing on a word processor cannot predict where a word will appear on a line, since formatting and hyphenation is not implemented until at a later stage, during typesetting. So far, so good. However, it can happen, especially in Irish, that a hyphen is a normal part of text, and not an indication to a typesetter of what to do when a line reaches the right hand side. Unless properly treated, as they say, this can cause the word processor to incorrectly interpret the hyphen as an instruction to break a word at that point, meaning that one can end up with a very unnaturally looking sentence with, for example, a single letter followed by a hyphen on one line, and the rest of the word on the next line.
For example, Tá an t-asal ina shuí (The donkey is sitting). Note the hyphen between the “t” and the “asal”. These should not be separated onto two different lines.
Now, to the point: It is possible to instruct the computer to treat a hyphen as a normal letter, something that would prevent it from breaking the word (Note that words are not split at arbitrary locations). What you end up with is a text string containing an embedded hyphen (and seen as such on the screen) but such that the entire string (before and after the hyphen) is locked together as a single “horizontal entity”, and therefore having to be placed in only one location, i.e. on a single line.
This is how you do it:
In Word and in LibreOffice/OpenOffice.org Writer
Press CNTL and SHIFT together, and then press the hyphen (“-”).
Note that OpenOffice.org Writer shows the hyphen on a shaded background (on the screen only; this is not printed), something that indicates that the processor “understands” the instruction. Word, although it has the same function, does not give any ready visible feedback like this to the user.
One should use the hard hyphen in cases such as this: (an) t-asal; (a) n-áiteanna; (an) t-uachtarán, and so on.