unable
Not able to do something because of limits or problems.
Unable means lacking the power, skill, resources, or capacity to do something. When you're unable to reach the top shelf, you physically can't get there without help. When a student is unable to attend class because of illness, circumstances prevent them from showing up.
The word points to a real limitation or barrier. Someone who is unable to solve a difficult equation lacks the knowledge or skill to do it. In contrast, someone who simply doesn't feel like trying has made a choice rather than facing a genuine obstacle. Being unable to swim means you haven't learned how yet. Being unable to lift a heavy box means it exceeds your strength.
The word often appears with “to” plus a verb: unable to finish, unable to remember, unable to decide. Sometimes circumstances make us unable to do things we normally could. A pianist with a broken hand becomes temporarily unable to play. A family might be unable to afford a vacation this year.
Recognizing when people are truly unable to do something matters. It helps you see when someone might need help, more time to learn a new skill, or a different approach. Being unable isn't the same as being unable forever; it describes a situation right now, which can often change with time, practice, or support.