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](https://www.officeequipmentmagherafelt.co.uk/ekmps/shops/e07db2/images/conte-a-paris-fusain-charcoal-drawing-pencils-1190-p.jpg)
Example: In apple product designers consistency follows not only logo they also follow consistency operation of same products.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh824DKn4fHyEV9VRpyLv6JEAmF1FrsI1DzgzZPSoeo3owd0CxEa3Qm_GEI7I5dK1Jlzdcbb7rSDchrbxpQI0f-oqx-SLc4V-YfBn-YIiir_CJ7bFZPeMr3QS0lUnGV9kyaCtpd44ZOLGdU/s640/apple-lineup.jpg)
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.