Difference between Chili and Pepper

From diff.wiki

Chilis and peppers tend to come up in recipes when we’re trying to make something with a bit of a kick. Sometimes, the term “chili peppers” also appears. How are chilis and peppers actually different from each other? Here, we will discuss the key points that segregate the two.

Chili can be used to refer to the chili powder that is commonly used in cooking, or the plant itself. When preparing food, chili is sometimes utilized because of the heat that it brings to food. Chilis are planted and cultivated and can be directly used in cooking, or dried and ground into powder and combined with other spices to make chili powder.

On the other hand, peppers can refer to various members of the genus, Piper. This includes the chili pepper, which can comprise different species of peppers used in cooking such as bell peppers, cayenne, and habanero. Pepper is also a word used to refer to the spice derived from dried, ground peppercorns. Rather than heat, they are more utilized for the savory flavor, aroma, and pungent characteristics they add to food.

Basically, when we are talking about the spices themselves, chili is used for heat while pepper is used for flavor and “spice”. In terms of agriculture, a chili is a pepper, but not all peppers are chilis. Both are members of the Nightshade family. 

Pepper Chili
Forms Whole chilis; powder as spice Whole specimens of  members of the Piper genus; powder as spice
In its complete form Mostly small, red and elongated; can be chopped or added whole to dishes Characteristics vary with the species; Most species are also used in cooking and can be added whole or chopped
In powder form Mostly blended with other spices to make chili powder; generally added during the cooking process to add heat Ground peppercorns are turned into black or white pepper; used during cooking for flavor or sprinkled on a complete dish
Source of powdered form Dried and ground chilis, possibly blended with other spices Dried and ground peppercorns
Taste Hot and prickly, varies with the type of chili Pungent, flavorful, spicy, sharp; taste can vary depending on the pepper and form
Scientific classification Species: Capsicum annuum Genus: Capsicum; numerous species including chili, bell peppers, and habanero
Source of Heat or Flavor Capsaicin Piperine; Capsaicin