In English, we don’t really have this. An ‘a’ looks like nothing in particular. The word ‘sun’ has no relationship to the sun we see, or the version we see mentally.
The field of semiotics was partially interested in this – the relationship between the word – the signifier – and the concept of the word – the signified. But occasionally it deals with the referent – the physical object. For instance, is there something inherently rabbit like about a rabbit? And if so, how can the French call it ‘lapin’ or the Spanish ‘conejo’?
The current orthodoxy is that there is no relationship between the word and the object it describes.
But a famous experiment overturns this – it offered participants two shapes – a round, curved shape and a spiky shape – and asked which one was named ‘kiki’ and which was ‘bouba’. In both English and Tamil speakers, 98% selected ‘bouba’ for the rounded shape, ‘kiki’ for the spiky. One explanation might be the sounds the vowels make in your mouth – ‘bouba’ involving a more rounded mouth, while ‘kiki’ requires taut hard shapes.
Onomatopoeic words – that suggest the sound of how they actually sound – are another possible example – see ‘splat’ ‘boom’ ‘squelch’. Other examples might be animal noises – how we have decided that a cat ‘meows’ and a dog ‘woofs’. Though I remember being shocked to find out that in French, a horse goes ‘hiiii’ instead of ‘neigh’.
You can see this in our attempts to form new words over social networking. Saying ‘lol’ may be replacing laughing in real life, but conversely, the abbreviation of ‘casual’ is harder to spell online – ‘cadge’ ‘cas’ ‘cajj’ ?
And, on another note, pictorial languages are especially interesting.
The Japanese symbol yu is part of the Japanese phonetic alphabet, hiragana. But on its own, it means ‘hot water’ – derived from the original natural ‘hot springs’ of the Japanese baths. When I look at this symbol, I remember it by seeing the stick like figure of a man standing in the middle of the swirl of the hot spring pool. Or another example is the Chinese symbol for man, a composite of the symbol for farmland (at the top) and power (at the bottom). A man being someone powerful working on the land. In one symbol, you see a snippet of cultural history, and a small insight into how speakers of that language see the world.