Modals in Formal Language

Can and Could

Can is used to express a request, an offer, or an invitation. It also expresses ability, permission, and possibility.

Examples:

Request:	“Devata, can you give us a child?”
Offer:	The old man says he can work in the farm.
Invitation:	You can come to the shrine to pray for a child.
Ability:	The old man can work on the farm.
Permission:	You can bring candles and flowers to offer to the gods.
Possiblity:	The children can become kings of their tribes.

Could is the past tense of can. It is used to express a more polite request, offer, or invitation.

Examples:

Polite request:	“Devata, could you please give us a child?”
Polite Offer:	“I could look after the children,” said the old woman.
Polite request:	Devata says the old couple could come to the shrine to pray for a child.
Ability:	The old man could work on the farm.
Permission:	You could bring candles and flowers to offer to the gods.
Possiblity:	The children could become rulers of their tribes.

Be able to is not strictly a modal since it consists of the main verb be, the adjective able, and the particle to. However, it is sometimes used to replace can and could to express ability.

May and Might

May is used when a speaker is not sure about something. It is also used to make a polite request or permission.

Examples:

Possibility:	The old couple may be visiting the shrine to pray for a child.
Polite request:	“May the great devata bestow a great blessing on us.”
Polite permission:	“You may go back to your former selves.”

Might is used when the speaker is not sure about something. It is also used as the past tense of may for requests and for making polite requests.

Examples:

Possibility:	The old couple might go to the shrine tomorrow.
Past form of may:	The old couple wanted to know if the great devata might grant them a child.
Polite request:	The old couple prayed, “Great devata, might we be granted a child?”