The term "unable to work" refers to a person's inability to perform their job duties due to physical or mental incapacity. There are several synonyms for this phrase that can be used interchangeably in different contexts. These include "not fit to work," "incapacitated," "disabled," "unable to perform," and "infirm." Other similar phrases include "out of commission," "off duty," "off the job," and "off work." These synonyms may have slightly different connotations depending on the context in which they are used, but all generally describe the same condition of being unable to fulfill work obligations.