Consistency:
  • It can be defined as a harmonious uniformity or agreement among things or parts. Designer is to create order, to make it easy for users to find the information they are looking for.
Image result for hp pencils using in drawing
 Example: In apple product designers consistency follows not only logo they also follow consistency operation of same products.
   
     Benefits of consistency:
  • Eliminates confusion.
  • Saves money and time.
  • Systems are usable and learnable when similar concepts are in similar way.
  • Focus on task instead of learning how it works every time they switch the content.
  • Ease in using the product.
     Types of consistency:
     There are four types of consistency
     1. Visual consistency:
  • Similar elements that are perceived the same way make up the visual consistency. It increases learnability of the product. 
  • Fonts, sizes, buttons, labeling and similar need to be consistent across the product to keep visual consistency.
     2. Functional consistency: 
  • Similar controls that are functioning the same way make up the functional consistency. 
  • It increases the predictability of the product. Predictability leads to users feeling safe and secure.
     3. Internal consistency:
  • This is the combination of both visual and functional consistency in your product design.
  • It improves the usability and learnability of the product.
  • Even when you introduce new features/pages users will have easy way using them as long as you keep the internal consistency.

   4. External consistency:
  • External consistency is when elements are consistent across multiple independent systems. This is more difficult to achieve because systems often do not observe a common design