1) Softness 
In software engineering, extensibility (not to be confused with forward compatibility) is a system design principle where the implementation takes future growth into consideration. It is a systemic measure of the ability to extend a system and the level of effort required to implement the extension. Extensions can be through the addition of new fu...
• (n.) The quality of being extensible; the capacity of being extended; as, the extensibility of a fiber, or of a plate of metal.
ability of a digital television system to support and incorporate extended functions and future advances in technology.
Ex·ten`si·bil'i·ty noun The quality of being extensible; the capacity of being extended; as, the extensibility of a fiber, or of a plate of metal. 
extensibility 1. The quality of being extensible. 2. The capacity of being extended; as, the extensibility of a fiber. Related 'tension' words at this tono- unit.