Rhagddodiad SI| Math | rhagddodiad yr uned  |
|---|
| Y gwrthwyneb | non-SI unit prefix |
|---|
| Yn cynnwys | quecto, ronto, yocto, zepto, atto, femto, pico, nano, micro, milli, centi, deci, null morpheme, deca, hecto, kilo, mega, giga, tera, peta, exa, zetta, yotta, ronna, quetta |
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 Ffeiliau perthnasol ar Gomin Wicimedia |
Rhagddodiad safonol wedi'i dderbyn gan system enwi rhyngwladol o'r enw System Rhyngwladol o Unedau (Ffrangeg: Le Système international d'unités; Saesneg: International System of Units)[1] ydy rhagddodiaid SI, sydd wedi eu seilio ar saith prif uned o fesur ac ar hwylustod y rhif deg (10):
Rhagddodiaid a safonwyd i'w rhoi o flaen yr Unedau
| Lluoswm
|
Enw
|
|
deca-
|
hecto-
|
kilo-
|
mega-
|
giga-
|
tera-
|
peta-
|
exa-
|
zetta-
|
yotta-
|
| Symbol
|
|
da
|
h
|
k
|
M
|
G
|
T
|
P
|
E
|
Z
|
Y
|
| Ffactor
|
100
|
101
|
102
|
103
|
106
|
109
|
1012
|
1015
|
1018
|
1021
|
1024
|
|
|
| Isddosbarthiad
|
Enw
|
|
deci-
|
centi-
|
milli-
|
micro-
|
nano-
|
pico-
|
femto-
|
atto-
|
zepto-
|
yocto-
|
| Symbol
|
|
d
|
c
|
m
|
μ
|
n
|
p
|
f
|
a
|
z
|
y
|
| Ffactor
|
100
|
10−1
|
10−2
|
10−3
|
10−6
|
10−9
|
10−12
|
10−15
|
10−18
|
10−21
|
10−24
|
Rhagddodiaid SI
| Rhagddodiad
|
Symbol
|
1000m
|
10n
|
Ffurf degol
|
Term Cymraeg
|
Term Saesneg
|
Derbyniwyd[1]
|
| iota-
|
Y
|
10008
|
1024
|
1000000000000000000000000
|
Septiliwn
|
Septillion
|
1991
|
| seta-
|
Z
|
10007
|
21
|
1000000000000000000000
|
Secstiliwn
|
Sextillion
|
1991
|
| ecsa-
|
E
|
10006
|
18
|
1000000000000000000
|
Cwintiliwn
|
Quintillion
|
1975
|
| peta-
|
P
|
10005
|
15
|
1000000000000000
|
Cwadriliwn
|
Quadrillion
|
1975
|
| tera-
|
T
|
10004
|
12
|
1000000000000
|
Triliwn
|
Trillion
|
1960
|
| giga-
|
G
|
10003
|
9
|
1000000000
|
Biliwn
|
Billion
|
1960
|
| mega-
|
M
|
10002
|
6
|
1000000
|
Miliwn
|
Million
|
1960
|
| kilo-
|
k
|
10001
|
3
|
1000
|
Mil
|
Thousand
|
1795
|
| hecto-
|
h
|
10002⁄3
|
2
|
100
|
Cant
|
Hundred
|
1795
|
| deca-
|
da
|
10001⁄3
|
1
|
10
|
Deg
|
Ten
|
1795
|
|
|
|
10000
|
0
|
1
|
Un
|
One
|
|
| deci-
|
d
|
1000−1⁄3
|
−1
|
0.1
|
Degfed
|
Tenth
|
1795
|
| centi-
|
c
|
1000−2⁄3
|
−2
|
0.01
|
Canfed
|
Hundredth
|
1795
|
| mili-
|
m
|
1000−1
|
−3
|
0.001
|
Milfed
|
Thousandth
|
1795
|
| micro-
|
μ
|
1000−2
|
−6
|
0.000001
|
Miliynfed
|
Millionth
|
1960[2]
|
| nano-
|
n
|
1000−3
|
−9
|
0.000000001
|
Biliynfed
|
Billionth
|
1960
|
| pico-
|
p
|
1000−4
|
−12
|
0.000000000001
|
Triliynfed
|
Trillionth
|
1960
|
| femto-
|
f
|
1000−5
|
−15
|
0.000000000000001
|
Cwadriliynfed
|
Quadrillionth
|
1964
|
| ato-
|
a
|
1000−6
|
−18
|
0.000000000000000001
|
Cwintriliynfed
|
Quintillionth
|
1964
|
| septo-
|
z
|
1000−7
|
−21
|
0.000000000000000000001
|
Chwetriliynfed
|
Sextillionth
|
1991
|
| iocto-
|
y
|
1000−8
|
−24
|
0.000000000000000000000001
|
Heptriliynfed
|
Septillionth
|
1991
|
- Cyflwynwyd y system ddegol am y tro cyntaf yn 1795 gyda dim ond chwe rhagddodiad. Mae'r dyddiadau eraill yn cyfeirio at y dyddiadau y cafodd y rhagddodiaid eraill eu derbyn yn swyddogol gan CGPM.
- Yn 1948 cafodd y micron ei dderbyn gan y CGPM; yn 1967 penderfynwyd ei hepgor.
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