©Isarint/Bigstock
Scallion is the term for an onion harvested early on in the life cycle before the bulb begins to swell.
Green onion is technically the term for an onion harvested during the next stage of the life cycle.
Green onions have a slightly more pungent flavor and bring more of that unique sharp onion character to the dish.
Spring onions have much more of that typical onion flavor and would easily overpower a dish if used raw.
©Studio Lucky/Bigstock