I exploded on Twitter, earlier in the week, as much as 140 characters will allow you to explode. It was after the nth report that I had heard, or read, discussing ISIS atrocities in the 'amphitheatre' at Palmyra. I admit that I have not been there, but so far as I know Palmyra has no amphitheatre. What it does have is a rather splendid theatre (above, photo Reuters).
The different is simple. In an amphitheatre the seat go all the way round in an oval (that's what the word basically means: amphitheatre). Here's the one at Arles:
In a theatre, the seats are in a semi circle, or sometimes a bit more than 'semi' and there is a stage at one end, as in the picture above.
The amphitheatre was a distinctively Italic/Roman invention; the theatre was found in both the Roman and Greek world.
So why get so cross about an innocent, if repeated, confusion? Why be a pedant?