frank

Free postage, a right exercised by governments (usually with definite article).

The notice on an envelope where a stamp would normally be found.

To place a frank on an envelope.

To exempt from charge for postage, as a letter, package, or packet, etc.

To send by public conveyance free of expense.

Honest, especially in a manner that seems slightly blunt; candid; not reserved or disguised.

"May I be frank with you?"

Unmistakable, clinically obvious, self-evident

"The research probes whether treating pre-diabetes with metformin can prevent progression to frank diabetes."

Unbounded by restrictions, limitations, etc.; free.