1) Am unable to 2) Common error message word 3) Exclusively Anglo word 4) Exclusively Saxon word 5) Is incapable of 6) Is not in a position to 7) Is unable 8) Is unable to 9) Lack the skill 10) Lack the wherewithal 11) Lacks the ability 12) Lacks the means to 13) Lacks the wherewithal 14) Lacks the wherewithal to 
• Am, is, or are, not able; -- written either as one word or two.
Can'not [ Can to be able + -not .] Am, is, or are, not able; -- written either as one word or two. 
interchange flash units and cameras. I.e. a Nikon speedlight on a Canon camera.