Meaning of the word fastness in English

What does fastness mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

fastness

US /ˈfæst.nəs/
UK /ˈfæst.nəs/

Noun

1.

how fast (= fixed) something is:

Example:
Test clothes for color fastness before washing.
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