Here is another pair of words with an identical meaning but subtly different uses. There’s a style warning at the end, too. We like a style warning, don’t we!
Both though and although mean” in spite of the fact that”, “however”, “but”. “Although he’s messy at home, he’s very organised at work”, “She was a plainly dressed woman, though with a flamboyant taste in hats”, “The dogs, though fierce in appearance, were friendly”.
Although is the more formal of the two. I prefer it to though at the beginning of a sentence, which is the traditional way of doing things. “Though he was firm, he was fair” just looks better to me as, “Although he was firm, he was fair”.
You cannot replace though with although in adverbial uses – “it was nice of him to write, though”. or with as or even – “she doesn’t look as though she’s reading that book, even though she says she is”
And finally, you shouldn’t start a sentence with either of these if it’s actually acting as a linking word between the previous sentence and this one: “He was firm. Although he was fair too”, or if it’s making a link between two concepts in the upcoming phrases: “Although he was firm. He was fair too”. Make sure both of the linked ideas are in the same sentence.