No, it means 'is'.
In phrases such as:
- Mae teigr yn y gegin - There is a tiger in the kitchen
there is no specific word meaning 'there' - it is not necessary in the Welsh. It could be translated as 'A tiger is in the kitchen', too.
Welsh and English equivalent phrases often do not translate word-for-word because the basic structure of the two languages is so different,
Sometimes people do insert 'na for 'there' in similar phrases in casual speech, but then it needs to be followed by a soft mutation:
- Mae 'na deigr yn y gegin
(We do not usually do that on this course)
In the "write down what you hear" exercise?
I'm fairly sure that those only allow one single spelling - the one of the original sentence.
(This sentence discussion has the Welsh on top and the English below, so in my experience, it's a sentence discussion for the top half of the incubator, i.e. either "translate Welsh to English" or "type what you hear" -- but not "translate English to Welsh" and so I think the accepted alternatives for that bottom half are irrelevant. This bit about synonyms is one we also struggle with on the Greek course where "type what you hear" can be tricky if there are multiple correct spellings that are pronounced identically or very similarly.)
Interesting. Unfortunately, as far as we know we have no control over which sentences are chosen by Duo for the various exercises.
In this case, though, it is easy enough just to stick to the spelling taught in the course, which is adre, the spelling normally taught on basic Welsh courses.