Of course this one comes under the “these words sound the same! Which on earth do I use?” category, as so many Troublesome Pairs do. What do you do if you’ve only heard the words spoken but want to write one of them (well, you look here or in a dictionary, but you know what I mean …).
So, here’s the difference:
A horde is a noun meaning a large group of people. It’s often used in a pejorative or slightly threatening sense (ravening hordes) but also in a positive, if slightly anachronistic way: “Hordes of people came to my tennis party!”
A hoard is a noun meaning a store of money or possessions. It’s usually used for something impressive and/or unusual, rather than just “some stuff”, for example a dragon will have a hoard of gold and jewels, and we had the Staffordshire Hoard archaeological find of golden and bejewelled items a few years ago. There’s a verb to go with this one: to hoard – to collect such things together, usually seen in a negative way to describe misers or people who can’t bear to throw anything away.
Interestingly, they do come from different routes: horde comes from the Turkish for (royal) camp, via Polish, whereas hoard comes from Germanic origins.
I used both words in one sentence in a post on my other blog today, as a little hint as to which troublesome pair I was going to post today – I wonder if any of my hordes of readers noticed …