A straat is a street- that's simple enough
A gracht (city-canal) is a waterway in the city with streets on
both sides of the water. The streets are lined with houses- ok
For instance, if you are on Egelantiersstraat and you don't see any canals, then you know that you are indeed on Egelantiersstraat. If you see a canal, then you are on Egelantiersgracht, or perhaps another gracht. Also, Egelantiersgracht runs along both sides of the canal.
This is perfectly logical.
However, a singel is by origin a water-filled moat
which surrounds a city for defensive purposes. When the city expands the
singel is incorporated in the city’s structure and cannot be
distinguished any more from a gracht, although the name ‘singel’ is usually maintained. You guessed it. There is a Singel here, and it looks just like a gracht- its on both sides of the canal!
Fortunately, a dijk is just a dike.
