Consistency

• Uniform Design.
• Key principle of life and design.

Types of Consistency:

• Visual Consistency.
• Functional Consistency.
• Internal Consistency.
• External Consistency.

Visual Consistency:

• Following same font, buttons and labeling.
• Honda as two different logos for two wheeler and four wheeler(no consistency).
• Suzuki as same logo for two wheeler and four wheeler. 

• Genesis power company as two different fonts in its logo

Functional Consistency:

• Same functionality through out the life.

Internal Consistency:

• Same functionality and design all over the applications.      
• Touch is internal and external consistency. 
• Touch functionality is selecting objects and moving between folders/pages.
• What ever Operating System the functionality of touch is same.

External Consistency:

• Operation and UI should be same all over the devices.
• Power buttons and volume buttons as same functionality in all phones and tab(android or ios platform).

Benefits:

• Eliminates Confusion.

• If UI is same on all devices it easy to operate.

• Reduces Learning.

• Windows has changed its UI in Windows 8 totally.
• It takes some time to learn its operation if we move from windows 8 to windows 10 .