We usually observe that the shape of most words is aribitrary, so if you did not know what horse referred to, you could not guess. And note that the word for this animal is massively different in a range of languages, so in French it is cheval, in Chinese it is mă, and in Malay it is kuda.
In contrast, we usually think of most signs, such as road signs, as iconic: they represent the concept pictorally (to a certain extent). For example, the sign on the right fairly obviously represents an aeroplane, and if you saw it on a road sign, you could immediately guess that it probably pointed to the location of an airport.
However, in reality, many signs are in fact arbitrary. Consider the next two. If you did not know which was which, there would be no way to figure out that the one on the left indicates something good and the one on the right shows an error. In fact, we often forget that this symbolism is arbitrary, and we get so used to seeing certain signs that we imagine there is something inherently 'good' contained in the tick sign and something 'bad' in the cross sign. In fact, there isn't. They are just arbitrary.
This arbitrariness of signs struck me when I observed the signs in an unfamiliar environment, while cruising along the Danube. Take the sign on the right. What does it indicate? No doubt it is perfectly obvious to anyone who travels up and down the river on a daily basis; but it is a complete mystery to an outsider like me.
And here's another one. I just looked up Wasser-Schutzgebiet, and it means 'water conservation'. But I am still somewhat mystified about what the symbols indicate.
"Artist=President Barack Obama"
21 hours ago