Any type of chemical/additive that allows for one liquid to be suspended inside another. In other words, it is an additive that allows for the formation of a stable emulsion. They have other uses as well, but those fall outside the purview of the website here. Generally speaking, emulsifiers have a hydrophobic component (such as a long-chain fatty acid) and a hydrophilic component. Vigorous mixing allows for the different liquids to be attracted to the corresponding components of the emulsifier in question. They share similarities with stabilizers.

Common emulsifiers include, but are not limited to, eggs, mustard, honey, agar, and more. Common uses of emulsifiers include their use in creating oil-in-water emulsions. For example, mayonnaise is one such emulsion.