steadfast

 
Pronunciation: /ˈstɛdfɑːst, -fəst/

adjective

  • resolutely or dutifully firm and unwavering: steadfast loyalty

Derivatives

steadfastly

adverb
[as submodifier]: they were steadfastly loyal

steadfastness

noun

Origin:

Old English stedefæst 'standing firm' (see stead, fast1)