How can you define a night terror with something else??

My DS is almost 26 months old and the last few nights he has been waking up crying and begging to be let out (we have a baby gate on his door).

Last night was the worst! He went to bed at 8.30, woke up at 12.30 crying, and 5 am crying... this may be normal to some others, but my son has slept through since he was 1 month old (except a few nights when he's been unwell)

Nothing seems to work to make him go back to sleep except a bottle of milk- which I really don't like doing!! His room isn't too dark, we leave the door open a little and the bathroom has a night light.

Is this a night terror??