"I am a teacher."

Translation: Athro dw i.

[EleriHunter]

Thing to remember is that, Welsh is a very old language, before the revolutionary Women's Right Movement. So we assume it's male, until specified.

[idiomasdaisuki]

Although, as in most/all other countries, teaching is predominantly (seen as) a women's profession in Wales - so assuming the female gender would seem more logical in this case...

[ibisc]

If the gender is unspeecified or known to be male, use athro, if known to be female, athrawes.

In this sentence either athro or athrawes can be used.

[idiomasdaisuki]

Oh yes, I'm familiar with the "if unspecified, use the masculine noun" concept - I'm simply pointing out that for traditionally female-dominated professions, the reverse would actually make more sense :)