Enables interaction in various contexts
I was at the zoo.
Helps convey meaning effectively
Expressing opinions
Making requests
You should drink eat warm soup.
I believe that we should go
You shouldn't swim.
Facilitates communication
You should go to the doctor.
I've got a toothache.
I've got a sore throat
I was at school
Please turn off the lights
I've got a headache.
Giving instructions
Could you pass me the salt?
I was at the library.
You shouldn't eat sweet.
I've got a cough.
I was at home.