Dw i’n ysgrifennu atoch I am writing to you

Sywch ar y ffaith ein bod wedi hepgor y rhagenw personol chi ar ôl atoch yn yr esiampl uchod.
Notice in the example above, that the personal pronoun chi has been left off the preposition atoch.

Mewn iaith ffurfiol, byddwn ni'n hepgor y rhagenwau personol - fi, ti, fe, hi, ni, chi, nhw– fel arfer, gan fod y terfyniadau'n ddigon i ddangos pa berson y byddwn ni'n ei olygu, e.e. 'at' ('ysgrifennu at berson').
In formal Welsh the personal pronouns - fi, ti, fe, hi, ni, chi, nhw– are usually omitted, as the endings are enough to show the person involved, e.g. ‘at’ (to write to a person).

SiaradYsgrifennuEnglish
ata iatafto me
atat tiatatto you
ato featoto him
ati hiatito her
aton niatomto us (the ‘n’ is changed to an ‘m’ in most 1st person plurals)
atoch chiatochto you
atyn nhwatyntto them (a ‘t’ is usually added to all 3rd person plurals)

Siarad > Ysgrifennu

Dweud wrthyn nhw > Dweud wrthynt to tell them

Edrych arnon ni > Edrych arnom to look at us

Siarad amdana i > Siarad amdanaf to talk about me

Rhai ohonoch chi > Rhai ohonoch some of you