06,08,2019 (1120)

A(AN) can be used like the word "per".

Examples:

• Apples currently cost $1.30 a pound.
• Cheetahs can run 60 miles an hour.
• You want $150 a person for the tour?

Do not use articles when generalizing about uncountable nouns and plural countable nouns.

Examples:

• Curiosity is a great trait. Uncountable
• Water is an important resource. Uncountable
• Vegetables are good for you. Plural countable

USE 16

English speakers often use THE plus a singular noun when they talk about or make generalizations about certain topics, including:

• musical instruments (the piano, the guitar, the flute)
• plants (the coconut palm, the saguaro, the baobab)
• animals (the leopard, the elephant, the lowland gorilla)
• inventions (the steam engine, the plane, the light bulb)
• currencies (the dollar, the euro, the yen)
• body parts (the head, the eye, the ear)

Examples:

• I play the piano.
• The sequoia tree is native to California.
• The dolphin is a very intelligent animal.
• The Wright brothers invented the airplane.
• Right now, the euro is stronger than the dollar.

https://www.englishpage.com/articles/articles_13.htm