"This is a cold bathroom."

Translation: هٰذا حَمّام بارِد.

[Rob396024]

I'm not sure I understand the significance of the little ا above the ه. I've not seen that before in standard written Arabic.

[alijsh]

It denotes that it's pronounced "haa", and not "hu", for example. It can't be written as هاذا. So, this diacritic is necessary to show the correct pronunciation. I don't know about normal writings but it's used in Koran and is a standard diacritic.

[stephen_zissou]

It's usually not written most of the time. Diacritics (harakat) are usually omitted, and this is one of them. The Koran is an exception. https://en.wikipedia.org/wiki/Dagger_alif