| etiolated(adjective, weak, thin, delicate, shaky) |
| exactingly |
| failed(adjective, unsuccessful) |
| failing health(noun, expression, disorder, collapse, disturbance) |
| fault(noun, disorder, weakness, illness, failing) |
| feebleness(noun, disorder, weakness, fault, illness) |
| feeling awful(expression, adjective, sick, unwell, enervated) |
| feeling rotten(expression, sick, infirm, unwell, poorly) |
| feeling terrible(expression, infirm, poorly) |
| feverish(mean, weak, down, sick, feeble) |
| fit(disorder, disease, collapse, disturbance, sickness) |
| flabby(adjective, weak, thin, delicate, shaky) |
| flagging(shabby, tacky, dingy, sordid, squalid) |
| flu(noun, disorder, disease, weakness, collapse) |
| frailness(noun, disorder, weakness, fault, illness) |
| frailty(noun, disorder, weakness, fault, illness) |
| fruitless(adjective, unsuccessful) |
| funny(mean, weak, down, ill, sick) |
| gaunt |
| gimpy |