Oh that's interesting. Good point. Although because they're used as phrases now, the は is often written as HA in romaji. You can see it either way I believe. Although in proper Japanese writing it will always be は.
Here's some more examples of は's usage as a particle (topic-marker).
kyou は samui desu. Today is cold.
ano basu は hayai desu. That bus is fast.
neko は kawaii desu. Cats are cute.
There's no English equivalent, so just remember that you put it after the topic of the sentence (today, bus, cat; whatever you're talking about), then you proceed to describe it.
you は (as for today), samui desu, it's cold.