fastness

名词 fastness:

1. a rate (usually rapid) at which something happens
   同义词：speed, swiftness
2. the quality of being fixed in place as by some firm attachment
   同义词：fixedness, fixity, fixture, secureness
3. a strongly fortified defensive structure
   同义词：stronghold

1. We guarantee the fastness of these dyes.
   我们担保这些染料不褪色。

fast.ness

n.（名词）
The condition or quality of being fast, especially:
迅速：快的状态或品质，特指
Firmness; security.
坚固；安全
Rapidity; swiftness.
快速；快捷
The quality or condition of color retention; colorfastness.
不褪色性：颜色保持的品质或状态；不褪色性

A secure or fortified place; a stronghold.
要塞：安全或设有防御工事的地方；堡垒
A remote, secret place.
偏远的，秘密的地方