I’m not able to make it fly high.
If I change not able to unable, will it retain the same meaning? When should I use not able and when unable?
Is the phrase fly high correct? Suppose I’m trying to make a helicopter fly high, but it’s not gaining altitude and I say “I’m not able to make it fly high.” to mean that.
As kiamlaluno says, using unable instead of not able doesn’t change the meaning of the sentence.
But idiomatically, in virtually every context, it would be more natural to say “I can’t [do something]”.
There’s nothing inherently wrong with “make it fly high”, but I think native speakers would probably say…
“I can’t make it fly any higher“
The implication there being you’ve made it fly as high as you can. Very likely the reason you’re saying anything at all is because it’s currently (or was recently) that high, and whoever you’re talking to knows how high that is/was. Otherwise, how does anyone know how high is “high”?
Source : Link , Question Author : T2E , Answer Author : FumbleFingers