Wild Radish (Raphanus raphanistrum) is a weedy plant of European origin who thrives in disturbed soil. Here in southern Maine, I most often find Wild Radish at the beach, growing above the high-tide line alongside American Sea-rocket, Saltwort, Beach Rose, and Beach Vetchling. Flowering plants stand about 2 feet tall and are topped with yellow, 4-parted flowers. On sunny days, Cabbage White butterflies frequently visit the blossoms.
Many parts of Wild Radish can be eaten, with the flavor of each part varying from mild (e.g., flowers) to strong (e.g., mature seeds). Leaves and tender growing shoots can be cooked as a pot-herb (though the coarse leaves are not high on my list of wild greens), flowers can be sprinkled on salads, young seed pods (next photo) can be eaten raw or cooked, and mature seeds can be used as a spice. Green Deane also writes of cooking and eating the peeled roots. I've yet to experiment with the ripe seeds or roots.
In the following photo, I've removed the 4 narrow sepals and 4 yellow petals from a single flower to reveal the pistil (center) and 6 stamens. This flower pattern of 4 petals and 6 stamens -- of which 4 are tall and 2 are short -- is true for Wild Radish and most members of the Mustard (Brassicaceae) family. According to Thomas Elpel, all mustard plants are edible (some 3,200 species worldwide), so if you notice this flower pattern on an unknown species, you can safely take a taste* to see if the flavor agrees with your palette.
*As a general guideline, I do not recommend sampling unknown plant species, but this is a case where identifying a plant to the family level (specifically the Brassicaceae family) is good enough. That said, I'll usually go the extra step to identify Mustards to the species level, because I enjoy keying out plants.