Mutation is a feature common to all of the Celtic languages, although none of them follow all of the same patterns. Mutation means that the first letter of a word is modified, by becoming another letter or combination of letters, or by vanishing entirely.
It is very important for the learner to be able to recognize and decode mutated words, not only because mutation is part of the grammar, but because if you don't, you will never find some words in the dictionary!
Some words that might mutate are:
Welsh has three types of mutation: soft, nasal and aspirate (aka spirant). The following are the tables of mutations, showing the initial letter and its mutated form, and some examples:
Original Mutated Example
c g "cath" (cat) becomes "gath"
p b "porth" (port) becomes "borth"
t d "teg" (fair) becomes "deg"
g (disappears) "gardd" (garden) becomes "ardd"
b f "bore" (morning) becomes "fore"
d dd "do+l" (meadow) becomes "ddo+l"
m f "merch" (girl) becomes "ferch"
ll l "llyn" (lake) becomes "lyn"
rh r "rhestr" (list) becomes "restr"
The changes below the line in the table do not occur in the limited soft mutation that occurs in
various contexts.
Original Mutated Example
c ch "car" (car) becomes "char"
p ph "potel" (bottle) becomes "photel"
t th "tad" (father) becomes "thad"
Original Mutated Example
c ngh "cwm" (valley) becomes "nghwm"
p mh "Pen-y-bont" (a place) becomes "Mhen-y-Bont"
t nh "ty+" (house) becomes "nhy+"
g ng "gwraig" (wife) becomes "ngwraig"
b m "brawd" (brother) becomes "mrawd"
d n "drws" (door) becomes "nrws"
There is one set of mutations that occurs that doesn't really have a name in the grammar books. It consists of forming the aspirate mutation of those consonants that can aspirate, and forming the soft mutation of anything else. Thus, it has the characteristics:
Original Mutated Example
c ch "carodd" (he loved) becomes "charodd"
p ph "poenodd" (he worried) becomes "phoenodd"
t th "torrodd" (he broke) becomes "thorrodd"
g (disappears) "gwyddodd" (he know) becomes "wyddodd"
b f "baglodd" (he stumbled) becomes "faglodd"
d dd "daliodd" (he continued) becomes "ddaliodd"
m f "mentrodd" (he ventured) becomes "fentrodd"
ll l "llyncodd" (he swallowed) becomes "lyncodd"
rh r "rhewodd" (he froze) becomes "rewodd"
If you can't find a word in the dictionary, look at its first letter and try to determine whether it has been mutated. Once you get to know the rules for mutation, you can tell by the context whether mutation has occurred. Here is a table that may help:
Initial Possible Mutation
letter original
b p soft
ch c aspirate
d t soft
dd d soft
f b or m soft
g c soft
l ll or gl soft
m b nasal
mh p nasal
n d nasal
ng g nasal
ngh c nasal
nh t nasal
ph p aspirate
r rh or gr soft
th t aspirate
w gw soft
[vowel] g soft
It may be helpful to note that
very few Welsh words begin with ch, dd, f, l (single l), r (without h), w, mh,
ng, ngh, nh, ph or th in their unmutated forms.
If none of the above yield a word in the dictionary, try putting a "g" before the first letter, especially if the first letter is a vowel, l or w.
Still another possibility is that an h has been prepended to a word beginning with a vowel. This is not usually considered a mutation, but it does occur. For instance, "enw" (name) becomes "ein henw" (our name). In this case, drop the h and see if you can find the resulting word.
Although mutations seem completely unnatural to English speakers, there is a little bit of logic behind some of them. For instance, when some American speakers think they're saying "in Colorado", what they're actually saying sounds more like "ingkolorado." In the Welsh phrase "yng Ngholorado", the mutation from "C" to "Ngh" simply approximates the spoken phrase.
(And if you're reading this and mumbling "yng Ngholorado" to yourself, trying to hear what it sounds like, remember that "yng" sounds like English "ung", not "ing". There, that's better.)