I could have chosen hiraeth, an over-documented word about longing that the Welsh like to show off, with just a hint of superiority. It cant be translated, we shout (or should I say whisper); and yet every language has its own flavoured word for longing or nostalgia.
As a 1960s language activist I saw it as being synonymous with our fate as a people, never getting rid of the shackles of servitude and inferiority. To be Welsh was to see things in negative. Thats why Id much rather go for glas.
Glas is packed with resonances, and has the ability to create different worlds. As a literary word it is a powerful double-edged word that is brimming with meanings. To start with it can mean blue, but it can also mean green. It can mean raw, fresh as newly-formed buds in spring, or blue as in skimmed milk. (Anybody acquainted with the sight of a fresh pail of milk will attest to its blue appearance.) The sea too can be azure or pale. The frisson of sea is often thought of when thinking glas, blue.
But glas in Welsh can also mean white. Confused? You should be! It can mean to gleam, to dazzle and sparkle. We say yng nglas y dydd (in the blue of the day) to mean early morning, just after dawn. It is blue, is it not, or is it gleaming with the freshness of a new day and mornings twilight?
We also use glas for thoroughness. To do ones very best would be gorau glas (blue best). Then there is that blue smile, glas wen, a smile full of insincerity and mocking.
The vein of light-coloured slate is also blue and its hue is never more acute than when the rain falls on the slates of north Wales, with its rainbow effect.
A dozen meanings, then, for just one small word. Its also a word in old Irish and other Celtic languages. And writing in a language which is still endangered, it gives me strength to know of all the rough-diamond edges it presents. And yet, I keep away from using it to mean death and mortality. Far better to think of it always as a word that gleams and shines, just like the splendour of writing through it a new dawn.