1. RATE

charge ▪ rent ▪ fee ▪ fare ▪ fine ▪ toll ▪ rental

These are all words for an amount of money that is charged or paid for something.

rate a fixed amount of money that is asked or paid for something:

a low hourly rate of pay

interest rates

charge an amount of money that is asked for goods or services:

an admission charge

rent an amount of money that you regularly have to pay for use of a building or room.

fee (rather formal) an amount of money that you have to pay for professional advice or services, to go to a school or college, or to join an organization:

legal fees

an annual membership fee

fare the money that you pay to travel by bus, plane, taxi, etc.fine a sum of money that must be paid as punishment for breaking a law or rule:

a parking fine

toll an amount of money that you have to pay to use a particular road or bridge.

rental an amount of money that you have to pay to use something for a particular period of time.

Rent or rental? In British English rent is only money paid to use a building or room: for other items use rental. In American English rent can be used for both, but rental is still more common for other item.

* Patterns

(a) rate/​charge/​rent/​fee/​fare/​fine/​toll/​rental for something

(a) rate/​charge/​rent/​fee/​toll/​rental on something

at a rate/​charge/​rent/​fee/​fare/​rental of…

for a charge/​fee

to pay (a) rate/​charge/​rent/​fee/​fare/​fine/​toll/​rental

to charge (a) rate/​rent/​fee/​fare/​toll/​rental

2. DISEASE

illness ▪ disorder ▪ infection ▪ condition ▪ ailment ▪ bug

These are all words for a medical problem.

disease a medical problem affecting humans, animals or plants, often caused by infection:

He suffers from a rare blood disease.

illness a medical problem, or a period of suffering from one:

She died after a long illness.

* disease or illness? Disease is used to talk about more severe medical problems, especially specific conditions and those that affect particular organs: 

Crohn's/​Parkinson's disease • heart/​kidney/​liver disease • heart/​kidney/​liver illness . Illness is used more generally and can refer to both severe and minor medical problems, and problems that affect mental health: a terminal/​life-threatening illness • a mild/​minor illness • mental illness • mental disease . 

Illness can be used about a period of time: a long/​short illness • a long/​short disease disorder (rather formal) a condition that causes problems with the way part of the body or brain works:

a rare disorder of the liver

A disorder is generally not infectious. Disorder is often used in the names of specific conditions affecting the brain, for example attention deficit disorder, bipolar disorder or post-traumatic stress disorder. When it is used to talk about physical problems, it is often used with autoimmune, blood, bowel and kidney, and these are commonly serious, severe or rare.