This is the 746th most frequent Hebrew word.
כושר
Fitness.
In this sentence, 'כושר' refers to physical fitness or the state of being in good physical shape.
אני שומר על כושר על ידי ריצות יומיות.
I maintain fitness by daily runs.
Here, 'כושר' conveys the ability or potential for something, in this case, excellence in expression.
למורה הזה יש כושר ביטוי מרשים מאוד.
This teacher has a very impressive ability to express themselves.
In this context, 'כושר' is used to imply a skill or competence in performing certain tasks.