Analysis for usage of the words a and the* in the phrase The cat sat on a mat.
The cat refers to a specific cat. A cat would imply any old flea-bitten cat dragged in from the streets spitting and scratching so violently you have to trap it in a sack to save the children from bloody scars and mental trauma. Surely, saying the specific cat renders it a cherished pet, loved and cared for by the entire family even though it too may be a cantankerous and lethal furball.
But let’s assume it’s lovely, the particular cat that sat on a unspecific mat. Let us, for the sake of this explanation, endow the cat with the benign character of a lightly toasted marshmallow and the weepiest eyes, cutest little pink nose and fluffiest, tuftiest ears ever to melt the stoniest of stony hearts.
“If it’s so damned cute why does it only have a poxy mat to sit on? Why not a plush, overstuffed cushion, eh?”
You may well ask, but it just doesn’t OK, it has a mat and probably not an especially pretty mat either because whoever wrote that line couldn’t even be bothered to make it the mat or a thing of any significance whatsoever. A thing so treasured it would come, eventually, to be taken for granted and yet if it was ever stolen it would instantly be missed, sending the entire household into a frenzy of wailing and gnashing of teeth at its loss.
So, a special mat it is not otherwise, such is the vanity of the writer, the mat would have been named ~ the Persian, the Berber, the Shag. We can only infer that it is not something so refined you feel instantly inadequate for walking upon it, rather as if you were walking on the prone body of a member of the Royal Family, something with a pile so deep and luxurious you could easily imagine losing an entire football team of short people amongst its tufts.
A mat more than likely refers to it being a manky scrap of rag. Is it any wonder, therefore, that the cat might be a little bit cross?
* a/an and the are articles, type of determiner and they go before a noun.