Welsh numerals

Template:Short description Template:Use dmy dates The traditional counting system used in the Welsh language is vigesimal, i.e. based on twenties where numbers from 11 to 14 are "x on ten", 16–19 are "x on fifteen" (though 18 is more usually "two nines"); numbers from 21 to 39 are "1–19 on twenty", 40 is "two twenty", 60 is "three twenty", etc.

There is also a decimal counting system, where numbers are "x ten y" unit(s), e.g. thirty-five (35) in decimal is (three ten five) while in vigesimal it is (fifteen – itself "five-ten" – on twenty).

Numerals

Number	Vigesimal system	Decimal system
0
1
2	(m), (f)
3	(m), (f)
4	(m), (f)
5
6
7
8
9
10	,
11	("one on ten")
12	,
13
14
15	,
16	("one on fifteen")
17
18	("two nines"/"three on fifteen")
19
20
21	("one on twenty")
22
23
24
25
26
27
28
29
30	("ten on twenty")
31
32
etc.
40	("two twenty")
41	("two twenty and one")
50		("half a hundred")
51
60	("three twenty")
61
70	("ten and three twenty")
71	("one on ten and three twenty")
80	("four twenty")
81
90	("ten and four twenty")
91	("one on ten and four twenty")
100
200
300
400
500
600
700
800
900
1000
2000
1,000,000
1,000,000,000
1,000,000,000,000

Variation in form

There is some syntactically and phonologically triggered variation in the form of numerals. There are, for example, masculine and feminine forms of the numbers "two" ( and ), "three" ( and ) and "four" ( and ), which must agree with the grammatical gender of the objects being counted. The numerals for "five", "six" and "hundred" (, and ) also have reduced forms (, , ) when they precede the object they are counting. The words for "ten", "twelve", and "fifteen" (, , ) have the alternative forms , , used before nasals (which may be the result of mutation) and, occasionally, vowels; these forms are becoming less common. Numerals change as expected according to normal rules of consonant mutation; some also trigger mutation in some following words (see below for details).

Use of the decimal system

The decimal system is widely used, but is rather uncommon for dates and ages. Larger numbers, however, tend to be expressed in this system e.g. 1,965 . In referring to years, on the other hand, the number of thousands is stated, followed by the individual digits, e.g. 1965 . This system appears to have broken down for years after 2000, e.g. whereas 1905 is , 2005 is .

The Welsh decimal counting system was devised by 19th-century Patagonian Welsh businessmen in Argentina for accountancy purposes. It was recommended to teachers for use in the first Welsh language schools in Patagonia by Richard Jones Berwyn in a book published in 1878. The system was later adopted in Wales in the late 1940s with the beginning of Welsh-medium education.

Use with nouns

The singular form of the noun is used with numbers, but for larger numbers an alternative form is permitted, where ("of") with the plural noun follows the number. Except where using this plural form, the noun is placed directly after the number but before any parts of the number that are added using ("on") in the traditional system.

Nouns are also mutated following many numbers. triggers the soft mutation () of feminine nouns, other than those beginning with "ll" and "rh", but not masculine nouns. and both trigger the soft mutation (ll and rh included). (but not ) and trigger the aspirate mutation. Several higher numbers (, , , , , and ) trigger the nasal mutation when used with ("year(s)"). The part of the number immediately preceding the noun will determine any mutation of the noun. In the plural form with , the soft mutation is used as is normal after .

The following example illustrates several of these points:

English	Thirty-six dogs
Traditional system	Template:Interlinear
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Decimal system	Template:Interlinear
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