Y ffurf lawn ar hyn fyddai - Mae’n rhaid i fi.... Yn llythrennol mae hyn yn golygu There is a necessity for me to…

Ar lafar, fyddwn ni ddim yn defnyddio 'mae'n' fel arfer.

Er mwyn gofyn cwestiwn byddwn ni'n defnyddio Oes...?, e.e:

Oes rhaid i fi…?                 Is there a necessity for me to..?
Mewn geiriau eraill            Must I?/ Do I have to?

Does dim rhaid i fi            There isn’t a necessity for me to
Mewn geiriau eraill             I don’t have to

Rhaid i fi beidio                There is a necessity for me to refrain from
Mewn geiriau eraill             I must not

Amserau eraill

Roedd rhaid i fi                   There was a necessity for me to
Mewn geiriau eraill              I had to

Bydd rhaid i fi                      There will be a necessity for me to
Mewn geiriau eraill              I will have to

In full this would be - Mae’n rhaid i fi…, which literally means -  There is a necessity for me to…

The -  mae’n, - is not usually used in speech.  

The question form of mae here is oes - is there? i.e:

Oes rhaid i fi…?          Is there a necessity for me to..?
In other words - Must I?/ Do I have to...?

Does dim rhaid i fi      There isn’t a necessity for me to.
In other words - I don’t have to

Rhaid i fi beidio        There is a necessity for me to refrain from.
In other words - I must not…
 

Other tenses 

Roedd rhaid i fi           There was a necessity for me to…
In other words - I had to…                           

Bydd rhaid i fi             There will be a necessity for me to…
In other words - I will have to…

Geiriau / ymadroddion sy'n debyg

Angen - Need

Mae arna i angen mynd     I need to go (Eitha ffurfiol)
Dw i angen mynd          I need to go (Ar lafar)

Gorfod - Have to

Dw i'n gorfod mynd       I have to go ( = 'Rhaid i fi fynd')
Mae hi'n gorfod dod       She has to come ( = 'Rhaid iddi hi ddod')

Nodwch: Does dim rhaid rhedeg yr arddodiad, na chofio am y treiglad, yma. Yn y De, bydd pobl yn ynganu 'Gorfod' fel petai'n 'Goffo'

Gorfodi rhywun i wneud rhywbeth - To force someone to do something

Mae Ffred yn gorfodi Sandra i adael      Ffred forces Sandra to leave

Other similar words / phrases

Angen - Need

Mae arna i angen mynd     I need to go (Somewhat formal)
Dw i angen mynd          I need to go (Colloquial)

Gorfod - Have to

Dw i'n gorfod mynd       I have to go ( = 'Rhaid i fi fynd')
Mae hi'n gorfod dod       She has to come ( = 'Rhaid iddi hi ddod')

Note: There is no need to conjugate the preposition, or to remember the mutation here. In the South, people pronounce 'Gorfod' as if it were 'Goffo'.

Gorfodi rhywun i wneud rhywbeth - To force someone to do something

Mae Ffred yn gorfodi Sandra i adael      Ffred forces Sandra to leave