Slender hollow green stems from a small onion relative, with a mild allium bite and none of the sulphurous heat of a raw onion.
What it does in a recipe: A gentle onion note plus a green garnish, used raw or added at the very end because heat destroys both the colour and the flavour. Pick the swap that covers that job — the ratios below are written so you can act on them without doing any arithmetic.
Snip chives with scissors rather than chopping them with a knife. A blade crushes the hollow stems and squeezes out the liquid that carries the flavour.
Cooking around an allergy? Diet tags here describe the ingredient itself, not any particular brand. Processed products change formulation without notice and shared production lines are common, so read the label on everything you use. A severe allergy is a medical matter — confirm with the manufacturer or your clinician rather than relying on a substitution chart.