"They have built extensively in the area."

Translation: Maen nhw wedi adeiladu yn helaeth yn yr ardal.

[GeoffBache]

Is it not allowed to contract to "adeiladu'n" here? Could have sworn I've seen an equivalent example.

[rmcode]

Yes, the contraction is perfectly correct, thanks for noticing the error. That's been added now.

[PeterCross7]

Can you use "yn eang" instead of "yn helaeth" here?