Relish

relish as a noun and in a culinary context, refers to a condiment or highly flavoured item of food taken with plainer food to add flavour and interest to it. An English example would be a small serving of pickled vegetables taken with plain bread and cheese.

A condiment may be a relish. However, it is more usual to refer to a condiment, e.g. mustard, as a condiment. Condiments are normally taken in small quantities, whereas relishes often come in mouthfuls and can usually be taken in conjunction with the main food, not necessarily in or on it; no one would just eat a spoonful of mustard, whereas one might very well do this with a sambal (corresponding closely to the meaning of relish) or chutney.