I gave 'Thief' and was given 'Thief' as an alternative suggestion. I'm going to be in bother for giggling in class.
I translated this as 'robber' - are the words 'thief' and 'robber' not interchangeable in Welsh?
Belatedly. A burglar is someone who breaks into a building with the intent of committing a crime. Any crime. A thief is specifically someone who steals, whether from your person or your house or wherever. A robber is a thief who applies force in the commission of the theft. So someone who steals something you have left on a table is a thief but not a robber. Someone who breaks into your house to steal things is both a thief and a burglar.