The short answer is: yes, and no. Also: it depends on who you ask. They are basically the same to begin with - they can all come from the same onion varietals. And while the names are often used interchangeably, the general concensus seems to be that they differ in maturity. Scallions are the youngest, and the bulb is therefore the smallest. Then come green onions, with a bit more of a bulb. And finally, spring onions - with an even more pronounced bulb. For it to be a "true" spring onion, it should also be planted in fall, and harvested in spring (hence the name). The taste is similar, with all of them having a mild onion flavor and therefore being great to use raw. However, scallions are milder than the other two, and true spring onions are much stronger in flavor than both green onions and scallins. In most cases, though, spring onions are just green onions with a different name. The onions shown in the pictures in this post are green onions.