What is an ablative absolute, and how do I translate one?

An ablative absolute is a noun + participle phrase which doesn't have any grammatical connection to the rest of the sentence, in which the noun and participle are in the ablative and agree in gender and number. For example:castro cincto, milites oppugnaverunt - with the camp having been surrounded, the soldiers attacked.In the sentence 'castrum oppugnabatur ab militibus cingentibus' (the camp was attacked by the soldiers who were surrounding it), there is no ablative absolute, as the noun and participle 'militibus cingentibus' are the agent and are connected to the rest of the sentence by 'ab'. The most obvious way to spot ablative absolutes is to recognise an ablative noun + participle, but make sure to check for this grammatical connection.When learning this construction, the easiest way to translate these is 'with x having y-ed' or 'with x having been y-ed' - in the first example, 'with the camp having been surrounded, the soldiers attacked'. When you get more confident, you can turn your translation into more natural English; for example 'when the camp had been surrounded, the soldiers attacked'. 'When', 'since' and 'after' are all common ways of translating ablative absolutes.