"Mi wna i wisgo het."
Translation:I will wear a hat.
"Mi" causes a soft mutation so the "g" is lost. If you wanted to use "gwna" you would have to say "Gwna i wisgo het".
As I understand it, it's a three-way choice between:.
- the unmutated 'gwna i' form;
- the 'mi (or fe) wnai' form, the 'mi' or 'fe' being what my Teach Yourself Welsh book calls 'meaningless particles' (but which in fact carry affirmative meaning); or
- the mutated form alone, i.e. 'wna i', which omits the 'mi' or 'fe' and is identical to the interrogative form (which itself can be preceded by the 'a' particle (which carries interrogative meaning, but is hardly ever used in normal speech) and to the negative form.
Mi/fe are optional in the short form future (mi wna i) and preterite (mi wnes i) tenses).
Mi (but not fe) also sometimes occurs with some forms of 'bod' (.e.g. 'mi ydw i' and' mi oedd o' and even 'mi roedd o') but this may be considered sub-standard.
I've never been able to work out which actual dialects go in for mi/fe. Fe is usually associated with the south, but forms with mi, considered northern, are by no means absent in southern dialects.
I have hard it suggested the forms may be less used these days, but I find myself eagerly turning to them as I find it helpful in practice to distinguish between affirmative and interrogative or negative speech forms. The unmutated form is not, as far as I can tell, a very frequent choice of natural speakers, but I'd be happy to be contradicted by those more in the know.