Welsh mutations
In Welsh, the first letter of a word can change. Cath (cat) can be gath, nghath or chath, depending on the word before it. These changes are called mutations, and there are three main ones: soft, nasal and aspirate.
New to mutations? Don't try to learn this whole page.
Start with the four sections marked Start here, and come back to the rest as your course reaches them. Your course will bring mutations in a few at a time, and if it does something differently, go with your course. Getting a mutation wrong rarely stops anyone understanding you.
Which letters changeStart here
Only nine letters mutate. Every other letter stays as it is. Each word is shown after ei (his), which causes soft mutation; fy (my), nasal; and ei (her), aspirate.
| Word | Softei = his | Nasalfy = my | Aspirateei = her |
|---|---|---|---|
| pen head | ei ben | fy mhen | ei phen |
| tad father | ei dad | fy nhad | ei thad |
| cath cat | ei gath | fy nghath | ei chath |
| bara bread | ei fara | fy mara | no change |
| drws door | ei ddrws | fy nrws | no change |
| gardd garden | ei ardd the g disappears | fy ngardd | no change |
| mam mother | ei fam | no change | no change |
| llyfr book | ei lyfr | no change | no change |
| rhaglen programme | ei raglen | no change | no change |
A handy pattern: soft mutation affects all nine, nasal affects the first six, and aspirate only p, t and c.
Soft mutation: the most common oneStart here
The most common mutation by far. These are the words and patterns that cause it. The mutated word is in bold, with the word it started as in brackets.
Feminine nouns after y / yr / 'r (the)
y gath (cath) · y ferch (merch) · yr ardd (gardd)
Only feminine singular nouns: y tad and y cathod don't change. Not ll or rh: y llaw, y rhaglen.
Adjectives after a feminine noun
cath fach (bach) · merch dda (da) · y gath ddu (du)
After a masculine noun they stay: ci bach.
A few adjectives that come before the noun
hen ddyn (dyn) · hoff fwyd (bwyd) · prif weinidog (gweinidog)
ei (his) and dy (your, to one person you know well)
ei dad (tad) · dy gath (cath)
Dy is the informal, singular "your". It goes with ti, for a friend, a family member, a child or a pet, and is often followed by di: dy gath di. To someone you'd speak to formally, or to more than one person, use eich (with chi) instead, and eich causes no mutation: eich cath chi.
These prepositions
am, ar, at, dan, dros, drwy, gan, heb, hyd, i, o, wrth
i Gaerdydd (Caerdydd) · o Fangor (Bangor) · ar ben (pen) y mynydd · am ddau (dau) o'r gloch · heb fara (bara)
yn before an adjective or a noun
Mae'r bwyd yn dda (da). · Mae Siân yn feddyg (meddyg). · yn gyflym (cyflym)
Not ll or rh: Mae'r ystafell yn llawn. Mae'r tocyn yn rhad. And not before a verb: Mae Siân yn canu.
dau / dwy (two) and un (one)
dau gi (ci) · dwy gath (cath) · dau lyfr (llyfr) · un ferch (merch)
Dau and dwy mutate every letter, ll and rh included. Un only mutates feminine nouns, and not ll or rh: un dyn, un llaw. More in Numbers.
mor (so), rhy (too)
mor dda (da) · rhy fawr (mawr)
Not ll or rh after mor: mor llawn.
neu (or) and pa (which)
te neu goffi (coffi) · Pa liw (lliw)?
The object of a short-form verb
Prynodd Siân gar (car). · Gwelodd Siân gi (ci).
The thing that is bought or seen mutates when it comes straight after a short-form verb and its subject.
Questions with a short-form verb
Welodd (Gwelodd) Siân y ffilm?
More in Asking a question.
Time phrases saying when
Dw i'n nofio bob (pob) dydd. · Mae'r siop ar gau ddydd (dydd) Llun.
Nasal mutation: after "my" and "in"Start here
Far fewer triggers, but you'll meet them every day.
fy (my)
fy nhad (tad) i · fy nghath (cath) i · fy mara (bara) i
In speech fy is often shortened to 'y or barely heard, but the mutation stays: 'y nhad i.
yn meaning "in"
yng Nghaerdydd (Caerdydd) · ym Mangor (Bangor) · ym Mhontypridd (Pontypridd) · yn Nolgellau (Dolgellau) · yng Ngwynedd (Gwynedd)
Yn itself changes to match: ym before m, yng before ng. Other letters stay: yn Llundain. Don't mix this up with the yn in Mae'r bwyd yn dda, which causes soft mutation.
blynedd (years) after some numbers
pum mlynedd (blynedd) · deng mlynedd (blynedd) · ugain mlynedd (blynedd)
Also blwydd (years of age) and diwrnod (day). The full list is in Numbers.
Aspirate mutation: after "her", "and" and "with"Start here
Only p, t and c change: to ph, th and ch.
ei (her)
ei chath (cath) hi · ei thad (tad) hi
a (and)
bara a chaws (caws)
â and gyda (with)
â chyllell (cyllell) · gyda phobl (pobl)
tua (about)
tua chant (cant) o bobl
tri (three), chwe (six)
tri chi (ci) · chwe phunt (punt)
Tri is for masculine nouns. The feminine tair causes no mutation: tair cath.
Mutations after numbersWhen you're ready
Numbers bring all three mutations together. The noun after a number stays singular (dau gi, two dogs), and some numbers change it:
un (1)
un ferch (merch) · un gath (cath)
Soft mutation, feminine nouns only. Masculine nouns, and feminine ones starting with ll or rh, stay as they are: un dyn, un llaw.
dau / dwy (2)
dau gi (ci) · dwy gath (cath) · dau fachgen (bachgen) · dwy ferch (merch)
dau lyfr (llyfr) · dwy law (llaw)
Soft mutation, on every letter. Dau goes with masculine nouns and dwy with feminine ones, but both mutate everything: unlike most soft-mutation triggers, ll and rh change too. The number itself mutates after "the": y ddau (dau), y ddwy (dwy) (the two of them).
tri (3)
tri chi (ci) · tri phlentyn (plentyn)
Aspirate mutation, masculine nouns only. The feminine tair causes no mutation: tair cath.
chwe (6)
chwe phunt (punt) · chwe chath (cath)
Aspirate mutation.
The rest: no change
pedwar ci · pum cath · saith ci · deg cath
Years: blwyddyn and blynedd
"Year" (blwyddyn) is one of the best examples of how much numbers can do. It's a feminine noun, so two, three and four use their feminine forms: dwy, tair, pedair.
- One year: un flwyddyn. Blwyddyn takes a soft mutation after un, as feminine nouns do.
-
Two years or more: Welsh switches to a special counting form, blynedd,
and that form mutates in turn:
- soft after dwy: dwy flynedd
- no change after tair, pedair and chwe: tair blynedd
- nasal after five, seven, eight, nine, ten and the others in the table below: pum mlynedd
| Years | Welsh | Mutation |
|---|---|---|
| 1 | un flwyddyn (blwyddyn) | Soft |
| 2 | dwy flynedd (blynedd) | Soft |
| 3 | tair blynedd | – |
| 4 | pedair blynedd | – |
| 5 | pum mlynedd (blynedd) | Nasal |
| 6 | chwe blynedd | – |
| 7 | saith mlynedd (blynedd) | Nasal |
| 8 | wyth mlynedd (blynedd) | Nasal |
| 9 | naw mlynedd (blynedd) | Nasal |
| 10 | deng mlynedd (blynedd) | Nasal |
| 12 | deuddeng mlynedd (blynedd) | Nasal |
| 15 | pymtheng mlynedd (blynedd) | Nasal |
| 18 | deunaw mlynedd (blynedd) | Nasal |
| 20 | ugain mlynedd (blynedd) | Nasal |
| 100 | can mlynedd (blynedd) | Nasal |
- Some numbers have a shorter form before a noun: pump → pum, chwech → chwe, cant → can, and deg, deuddeg, pymtheg become deng, deuddeng, pymtheng before mlynedd. So deng mlynedd is simply "ten years".
- Age works the same way with blwydd: dwy flwydd (blwydd) oed, tair blwydd oed, pum mlwydd (blwydd) oed.
- So does diwrnod (day): dau ddiwrnod (diwrnod), tri diwrnod, pum niwrnod (diwrnod).
- With the newer way of counting (un deg un, tri deg…), bigger numbers usually take o and the plural instead: tri deg o flynyddoedd (blynyddoedd) (thirty years).
- For counting, the old and new systems, and ordinals (first, second, third), see Welsh numbers.
Words starting with a vowel: adding hWhen you're ready
Some words that cause mutation add an h to a word starting with a vowel instead.
ei (her), ein (our), eu (their)
ei henw (enw) hi · ein hathro (athro) ni · eu henwau (enwau) nhw
Compare ei enw (his name): ei meaning "his" never adds h. So ei enw and ei henw tell you whose name it is.
Short "his", "her" and "their" (i'w, a'i, gyda'i)When you're ready
You'll mostly meet these from Canolradd. At Mynediad, just knowing ei and eu is plenty.
In short: ei (his, her) and eu (their) often lose a letter or two when they follow a short word like i (to), a (and) or gyda (with). They still mean the same, and still cause the same mutations.
After a word ending in a vowel, ei (his, her) shortens to 'i, and eu (their) to 'u. After i (to, for) that would give an awkward "i'i", so Welsh uses an old short form, 'w, for all three: i'w. The mutations stay exactly as they are for the full words: soft for "his", aspirate for "her", none for "their".
After a vowel: 'i and 'u
gyda'i fam (mam) · a'i thad (tad) · o'u tŷ
with his mother · and her father · from their house
After i (to, for): i'w
i'w dad (tad) · i'w thad (tad) · i'w tad
to his father · to her father · to their father
Because 'i and i'w look the same for "his", "her" and "their", the mutation is often the only clue. To choose it yourself, ask what the word refers back to. With gweld (see):
- one masculine thing: Mae'r castell i'w weld (gweld) (the castle can be seen);
- one feminine thing: Mae'r eglwys i'w gweld (the church can be seen);
- more than one of anything: Mae llawer o fannau (mannau) i'w gweld (there are lots of places to be seen).
The h before a vowel stays too: gyda'i henw (enw) hi (with her name), i'w hathro (athro) nhw (to their teacher).
Saying "didn't": the mixed mutationWhen you're ready
When a short-form verb is made negative, p, t and c take the aspirate mutation, and the other letters take the soft.
p, t, c → aspirate
Chlywodd (Clywodd) Siân ddim byd. · Thalodd (Talodd) Siân ddim.
Other letters → soft
Welodd (Gwelodd) Siân ddim byd. · Ddaeth (Daeth) neb.
Asking a questionWhen you're ready
In short: when a question starts with a short-form verb (one with its own ending, like darllenaist or gwelodd), the verb takes a soft mutation.
Statement
Question
Darllenaist ti'r llyfr neithiwr.
You read the book last night.
Ddarllenaist (Darllenaist) ti'r llyfr neithiwr?
Did you read the book last night?
Gwelodd Siân y ffilm.
Siân saw the film.
Welodd (Gwelodd) Siân y ffilm?
Did Siân see the film?
Prynoch chi fara.
You bought bread.
Brynoch (Prynoch) chi fara?
Did you buy bread?
Byddi di yno.
You'll be there.
Fyddi (Byddi) di yno?
Will you be there?
Why? In careful written Welsh these questions start with a little word, a, which causes a soft mutation: A ddarllenaist (darllenaist) ti'r llyfr? In speech the a is usually left out, but the mutation stays. So the mutation is what turns the statement into a question, along with your voice going up at the end.
- You'll know some already: Ga (Caf) i goffi? (May I have a coffee?) and Allwch (Gallwch) chi helpu? (Can you help?) are the same pattern.
- Questions with the long forms don't mutate: Wyt ti'n darllen?, Ydy hi'n bwrw glaw? They have their own question words instead.
- Compare saying "didn't": there p, t and c take the aspirate mutation (Phrynoch (Prynoch) chi ddim bara), but in a question everything takes the soft (Brynoch (Prynoch) chi fara?).
Set phrases to learn as they are
Some mutations are easiest to learn as part of a whole phrase rather than as a rule. You'll hear these all the time, so just learn them the way they're said.
weithiau (gweithiau)
sometimes
Always mutated: you'll never hear it as gweithiau.
bob (pob) dydd
every day
Time phrases saying when take a soft mutation.
ddydd (dydd) Llun
on Monday
The same: when it happens.
ganol (canol) dydd
at midday
The same again.
o dro (tro) i dro (tro)
from time to time
o and i both cause a soft mutation.
wrth gwrs (cwrs)
of course
wrth causes a soft mutation.
da dros ben (pen)
really good, extremely good
dros causes a soft mutation.
ers blynyddoedd lawer (llawer)
for many years
llawer after the noun, rather than llawer o before it, mutates. A little formal: in conversation, ers llawer o flynyddoedd or just ers blynyddoedd.
droeon (troeon) lawer (llawer)
many times
The same pattern as blynyddoedd lawer.
nos da
good night
No mutation, even though nos is feminine: d doesn't mutate after s. Not nos dda.
How mutations sound in everyday speech
The rules above are the standard ones. In everyday spoken Welsh, you'll notice some differences:
- The aspirate mutation is often left out after a, â, gyda and tua. You'll hear bara a caws. It's kept most consistently after ei meaning "her".
- In negative short-form verbs, many speakers use the soft mutation for every letter, so you may hear Glywodd Siân ddim byd.
- Fy often shrinks to 'y, while the nasal mutation stays.
None of these will stop you being understood. Your course or tutor will tell you which forms they want you to use, and in an exam, the standard forms are the safe choice.
Common questions
What are the three Welsh mutations?
Soft (cath → gath), nasal (cath → nghath) and aspirate (cath → chath). The first letter of a word changes because of the word before it, or because of the word's job in the sentence.
Why does cath become gath?
That's soft mutation. Cath is a feminine noun, so it mutates after the article: y gath. It also mutates after ei meaning "his" (ei gath) and after dwy (dwy gath).
Why doesn't llaw mutate after y?
Feminine nouns beginning with ll or rh don't take the soft mutation after the article: y llaw, y rhaglen. The same exception applies after yn before an adjective (yn llawn) and after un (un llaw).
Will people understand me if I get a mutation wrong?
Yes. A missed mutation rarely stops you being understood. Mutations make your Welsh sound natural, and they come with practice. Most learners pick them up gradually rather than all at once.
Why is it i'w weld in one sentence and i'w gweld in another?
I'w is i (to) with ei or eu, and the mutation depends on which: soft after "his" (i'w weld, for one masculine thing), none for "her" before g, and none for "their" (i'w gweld, for something feminine or plural). Ask what is being seen.
Why does the verb change in a question?
A question that starts with a short-form verb takes a soft mutation: Darllenaist ti'r llyfr (you read the book) becomes Ddarllenaist ti'r llyfr? (did you read the book?). In written Welsh the question starts with a, which causes the mutation; in speech the a is dropped but the mutation stays.
See mutations in your own words
Flashcards Cymraeg writes example sentences for the vocabulary from your course, and Explain breaks any sentence down word by word, including which mutation is happening, and why.