A number of verbs commonly make use of 'i' to indicate a person or object who is the direct recipient of an action, for example:
eisiau i chi; ...want you to...
Rwyf eisiau iddi ddod i'r parti.
I want her to come to the party.
hoffi i chi; ...like you to...
Bydden ni'n hoffi i'r staff fod yn fwy cyfeillgar i gwsmeriaid.
We would like the staff to be more friendly to customers.
gwneud i chi; ...make you...
Bydd y brifysgol yn gwneud i chi dalu am yr offer labordy.
The university will make you pay for the laboratory equipment.
gadael i chi; ...leave you to...
Rhaid i chi fy ngadael i orffen y garddio.
You must leave me to finish the gardening.
caniatáu i chi; ...allow you to...
Bydd y ffermwr yn caniatáu i chi groesi'r cae.
The farmer will allow you to cross the field.
disgwyl i chi; ...expect you to...
Mae'r cynghorydd yn disgwyl i ni bleidleisio drosto fe.
The councillor expects us to vote for him.
gofyn i chi; ...ask you to...
Gwnaethon ni ofyn i'r adeiladwr atgyweirio'r to.
We asked the builder to repair the roof.
addo i chi; ...promise you that..
Gwnaethon nhw addo i'r trefnydd y byddent yn dod i'r digwyddiad.
They promised the organiser that they would come to the event.
In some cases an action is carried out on an object, then the preposition 'i' is used to specify who is affected as a result:
anfon --- i chi; send --- to you
Byddaf yn anfon llythyr i'r cwmni.
I will send a letter to the company.
rhoi --- i chi; give --- to you
Mae hi'n rhoi'r llyfrau i'r siop elusennol.
She is giving the books to the charity shop.
gwerthu --- i chi; sell --- to you
Maen nhw'n mynd i werthu'r paentiad i amgueddfa.
They are going to sell the painting to a museum.
talu --- i chi; pay --- to you
Roedd yn rhaid i mi dalu £200 i'r garej am yr atgyweiriadau.
I had to pay £200 to the garage for the repairs.
cynnig --- i chi; offer --- to you
Mae'r gwesty'n cynnig pris arbennig i gwsmeriaid busnes.
The hotel offers a special price to business customers.
dangos --- i chi; show --- to you
Roedd yr athro cemeg yn dangos yr arbrawf i'r myfyrwyr.
The chemistry teacher was showing the experiment to the students.
estyn --- i chi; extend -- to you
Hoffwn ni estyn croeso cynnes i'n hymwelwyr.
We would like to extend a warm welcome to our visitors.