One of the most amusing quirks of growing up in Wales is that many students who stay in Welsh-language education throughout high-school won’t know the English words for certain scientific and technical vocabulary. While, as a general rule, all Welsh speakers today also speak English fluently, there are often certain blind spots for words you’d never hear outside of an educational context.
I was chatting about this recently with a friend I went to school with, and one English word that she always takes a moment to process is variable. In Welsh, this is newidyn. The plural is newidynnau in most dictionaries and in my experience, though Geiriadur yr Academi (the Welsh Academy Dictionary) lists newidion instead.
newidyn
variable
This masculine noun is a relatively new word in Welsh, adopted in the 20th century. It comes from newid (change), with the suffix –yn that can be used, among other things, to mean a thing.
Unlike its English equivalent, newidyn cannot function as an adjective. There are various options for this depending on what you mean. For example, for variable / changeable weather I would say tywydd newidiol, but overall I come across amrywiadwy more often. A person who is variable and fickle in terms of their mood and demeanour is oriog, anwadal or di-ddal.
In gwyddoniaeth (science), when conducting an arbrawf (experiment), you will need to have distinguished between the newidyn annibynnol (independent variable) that you are changing, the newidyn dibynnol (dependent variable) that you are measuring, and the newidynnau rheolydd (control variables) that must be kept consistent.
When performing these kinds of arbrofion (experiments) in my TGAU Gwyddoniaeth (GCSE Science) classes, we’d also use words like ymchwiliad (investigation), canlyniadau (results), tystiolaeth (evidence), afreolaidd (irregular), cymedr (mean), asesiad risg (risk assessment), tabl (table, though a physical table is bwrdd), mesur (measure), and the wonderful hapgyfeiliornad (random error).
Mae cydberthyniad cryf rhwng y ddau newidyn.
There is a strong correlation between the two variables.
Of course, newidynnau are used in mathamateg too. Here, they can be used to dynodi (denote) unknown information in a hafaliad (equation) that we need to datrys (solve), or the possible values of an element of a fformiwla (formula).
And though the letter x doesn’t appear in the Welsh gwyddor (alphabet), it’s put to good use as a newidyn in mathamateg whatever iaith (language) you speak.
In the branch of mathamateg known as ystadegaeth (statistics), there are a lot of different kinds of newidynnau. In the first instance you can distinguish whether something is a newidyn ansoddol (qualitative variable / categorical variable) or a newidyn meintiol (quantitative variable). The former is disgrifiadol (descriptive) and the latter is rhifiadol (numerical).
Newidynnau meintiol (quantitative variables) can be further subdivided into newidynnau arwahanol (discrete variables) and newidynnau di-dor (continuous variables).
While a newidyn arwahanol (discrete variable) has a limited number of possible gwerthoedd (values) – a common example is maint esgidiau (shoe size) – a newidyn di-dor (continuous variable) can have any gwerth (value) within an amrediad (range), with infinite possibilities.
Other kinds of newidyn you may have come across include a newidyn ffug (dummy variable), a newidyn offerynnol (instrumental variable), or my personal favourite, a hapnewidyn (random variable).
Heb y cysyniad o newidynnau, byddai calcwlws yn amhosibl.
Without the concept of variables, calculus would be impossible.
So as you can see, the word newidyn is well-used by Welsh gwyddonwyr (scientists) and mathamategwyr (mathematicians).
But did you know that its first appearance in the language was under a very different guise? In 1860, some time before the word was widely adopted as a technical term, Geiriadur Prifysgol Cymru (the Welsh University Dictionary) records it being used to mean changeling, a fairy child given by the tylwyth teg (fair folk) in replacement of a kidnapped human baban (baby).
Here, the suffix –yn takes on a different sense – it’s being used as a diminutive, so newidyn literally means not a change thing but a little changed one. The term isn’t used today, since we have the much less concise plentyn cyfnewid (exchange child) instead, and besides, it would be very confusing. It’s a fun little nugget of linguistic history nonetheless.
