Supplementary Goods

Definition – Supplementary goods are two goods that are used together. For example, if you have a car, you also need petrol to run the car. If you have a tv, a supplementary good would be an Amazon widget which allows you access to a much greater range of tv programmes.

Examples of supplementary good

  • Android phone and Android App. Here the app is a supplement to your phone.
  • Car and superlight tyres. The superlight tyres go with the car – they make the experience better, but are not necessary to complement the car, you can survive without the extra light tyres.

Definition of the word supplementary

The definition of supplementary is something that is added on, or that completes something. (dictionary)

Supplementary goods have a negative cross elasticity of demand. E.g. price of petrol goes up, demand for petrol and cars goes down.


An Android App is no good without an Android Phone. They are supplementary goods.

Complementary good

A very similar term is ‘complementary good‘ A complementary good is the same principle of two goods being used together. The difference is that complementary goods often need each other to function. If you have a printer, the complement is the printer ink. If you just had printer ink, it would be not much use without the printer.

Not to be Confused with Substitute Goods

Substitutes are two goods which could be alternatives.

For example, if you buy a gas cooker, the substitute is an electric cooker. If you buy Buxton mineral water, the substitute is Highland Spring mineral water.

Substitute goods have a positive cross elasticity of demand. A higher price of Buxton water leads to higher demand for Highland spring.

11 thoughts on “Supplementary Goods”

  1. So are complementary and supplementary goods the same? My Social Studies teacher has them both separate on our vocabulary list, and we have to write all the definitions to give to her, so now I’m confused.

    • Hello Ahmed,
      Supplementary goods are those goods that have alternatives or options to them. So that, you either choose one or the other and still achieve same purpose or satisfaction. For instance, Crest toothpaste & Colgate toothpaste.
      While Complimentary goods are those goods that need (though not at all times) another good to function. There is an interdependence between both. A common example is Printer and Printer-ink. The ones that are complimentary but can as well function independently includes; tea and sugar, coffee and cream. Reason is, although they go together but you could choose not to have your tea with sugar or your coffee with cream. But the printer can not function without a printer-ink, so they are perfect compliments.

  2. Please can someone explain to me the clear difference between Supplementary goods and Substitute goods. In one of the submission i came across, someone posits that Supplementary goods are Alternative goods one can chose from to satisfy a given want. If Substitute goods are equally Alternative goods what is the difference between them?

    • Supplementary Goods or Complementary Goods are goods that are used together. E.g. shoes and socks, knife and cutting board,…Remember, complementary sounds like complete, so in a sense, the products will complete each other (it would make more sense if they go together). Because of this, if the demand of a good increases, the demand of its supplementary goods or complementary goods will also increase as they usually go together. The relationship between complementary goods are directly proportional.

      Substitute Goods on the other hand, are goods that can replace each other as they have the same use. E.g. petrol and diesel, McDonald’s and Burger King,…Because of this, if the demand of a good increases, the demand of its substitute will decrease as people need less of its substitute goods. The relationship between substitute goods are inversely proportional.

      I hope this clear your understanding 🙂

  3. No, they are not. Many people are confused about this so let me clear one thing.

    Supplementary goods = complementary goods. They are goods that are used together. E.g. shoes and socks, knife and chopping board.

    Substitute goods are goods that can replace each other since they have similar uses. E.g. McDonald’s and Burger King, petrol and diesel.


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