Computer applications such as 'Google Translate' and the grammar checker 'Cysill' can be a great help in applying treigladau correctly. However, it may sometimes be necessary to write a document in Welsh by hand with the help of only a pocket dictionary. In this case, a strategy for checking treigladau is needed. The sequence shown below might be used as a check list:
1. Treigladau related to prepositions
A treiglad meddal is produced by am, ar, at, dros, trwy, dan, wrth, o, i, heb, tan, gan:
Aethon ni dros gae a thrwy goedwig i bentref.
We went over a field and through a forest to a village.
A treiglad meddal is applied to a posessed item indicated by gan:
Mae gan y myfyriwr gasgliad mawr o lyfrau.
The student has a large collection of books.
A treiglad trwynol is produced by yn ('in').
Mae'r digwyddiad yng Nghanolfan y Mileniwm yng Nghaerdydd.
The event is in the Millenium Centre in Cardiff.
A treiglad meddal may be required with compound prepositions, depending on the second preposition of the pair:
Gwnaethon ni redeg ar draws traeth o dan glogwyn.
We ran across a beach underneath a cliff.
A treiglad llaes is applied after â, gyda, tua:
Ar ôl tua phum munud gadawon ni, gyda chyfarwyddiadau
i ddod â thocynnau.
After about five minutes we left, with instructions to bring tickets.
2. Treigladau related to nouns and adjectives
A treiglad meddal is applied to a feminine singular noun after the article y ('the'), and a treiglad meddal is applied to each adjective or adjectival noun following a feminine singular noun:
Gwnaethon ni groesi'r bont reilffordd fawr rydlyd.
We crossed the large rusty railway bridge.
A treiglad meddal is applied to a noun preceded by an adjective:
Roedd yr hen dref yn brif ganolfan ar gyfer gwahanol ddiwydiannau.
The old town was a main centre for different industries.
Mae'r heddlu'n stopio unrhyw gerddwyr.
The police are stopping any pedestrians.
3. Treigladau related to possessive pronouns
A treglad trwynol is applied after fy ('my'):
Gwnaeth e cyfarfod â fy nhad a fy mrawd yn y cyngerdd.
He met my father and my brother at the concert.
A treiglad meddal is applied after dy ('your' familiar)
Mae lle yn y garej i dy gar a dy feic modur.
There is room in the garage for your car and your motorbike.
A treiglad meddal is applied after ei ('his/its' referring to a masculine noun)
Dychwelodd John i'w dŷ gyda'i wraig.
John returned to his house with his wife.
A treiglad llaes is applied after ei ('her/its' referring to a feminine noun)
Lansiodd Jane ei chwch ar ei thraeth agosaf.
Jane launched her boat at her nearest beach.
4. Treigladau related to verbs
A treiglad meddal is applied after the particle fe (South Wales) or mi (North Wales) which can proceed the verb to indicate a positive statement:
Fe wahoddodd y rheolwr y staff i gyfarfod.
Mi wahoddodd y rheolwr y staff i gyfarfod. The manager invited the staff to a meeting.
A treiglad meddal is applied to a verb beginning a question:
Ddringoch chi'r Wyddfa yn ystod eich ymweliad â Chymru?
Did you climb Snowdon during your visit to Wales?
A brynwch chi fwyd yn y dref y prynhawn yma?
Will you buy food in town this afternoon?
The treiglad meddal is applied whether or not the interrogative marker 'a' is present.
A mixed treiglad llaes/meddal is applied to a negative verb beginning a sentence. The treiglad llaes is applied where possible, and the treiglad meddal in other cases:
Ni chanodd e'r anthem genedlaethol. Chanodd e mo'r anthem genedlaethol. He did not sing the national anthem.
Ni ofynnais ynglŷn â'r gwaith cartref. Ofynnais i ddim ynglŷn â'r gwaith cartref. I did not ask about the homework.
The mixed treiglad llaes/meddal is applied with any of the possible negative verb patterns: ni..., ...mo, ...ddim.
5. Treigladau related to conjunctions
A treiglad llaes is applied after the conjunction a (and):
Teithion ni ar awyren a chwch a thrên.
We travelled on a plane and a boat and a train.
A treiglad meddal is applied after the conjunction neu (or):
Mae'r cwmni wedi'i leoli yn Abertawe neu Gaerdydd.
The company is based in Swansea or Cardiff.
A treiglad meddal is applied after pan (when), tan (until):
Roedden ni'n cerdded trwy'r pentref pan welon ni'r hysbysiad.
We were walking through the village when we saw the notice.
Dylech chi aros tan gaiff y car ei drwsio.
You should wait until the car is repaired.