Grime. You can hear the blackness of the curd under your fingernails (where on earth did that come from?) or the sour grey stuff that's making those towels hang so limply from their hooks.
Grime is a word with a touch of evil magic about it. How else can something that appeared to be quite acceptably clean an hour ago suddenly become become dulled and weighty with weeks of accumulated dirt?
I really can't think of any explanation other than magic. Bad, bad magic. Just don't expect the magic to work the other way, that's all.
Photo 'Grime and Gleam' by Martin Addison. (But don't expect The Gherkin to stay clean for long.) The church is St Botolph in Aldgate, London.
Grime is also, apparently, a sort of music invented in the East End of London. My dictionary tells me it's a mixture of garage, hip-hop, rap and jungle.
I'm sure that definition will be helpful to many people around the world.
If not, at all, to me.
Thing Not To Do Today: be grimy. This word comes from the Middle Dutch grime, and might be something to do with the Old English grīma, which means mask.