The difference between Bill and Greenback

Bill as a noun:

Any of various bladed or pointed hand weapons, originally designating an Anglo-Saxon sword, and later a weapon of infantry, especially in the 14th and 15th centuries, commonly consisting of a broad, heavy, double-edged, hook-shaped blade, with a short pike at the back and another at the top, attached to the end of a long staff.

Bill as a noun:

A cutting instrument, with hook-shaped point, and fitted with a handle, used in pruning, etc.; a billhook.

Bill as a noun:

Somebody armed with a bill; a billman.

Bill as a noun:

A pickaxe, or mattock.

Bill as a noun (nautical):

The extremity of the arm of an anchor; the point of or beyond the fluke (also called the peak).

Bill as a verb (transitive):

To dig, chop, etc., with a bill.

Bill as a noun:

The beak of a bird, especially when small or flattish; sometimes also used with reference to a platypus, turtle, or other animal.

Bill as a noun:

A beak-like projection, especially a promontory.

Bill as a noun:

Of a cap or hat: the brim or peak, serving as a shade to keep sun off the face and out of the eyes.

Bill as a verb (obsolete):

To peck.

Bill as a verb:

To stroke bill against bill, with reference to doves; to caress in fondness.

Bill as a noun:

A written list or inventory. (Now obsolete except in specific senses or set phrases; bill of lading, bill of goods, etc.)

Bill as a noun:

A document, originally sealed; a formal statement or official memorandum. (Now obsolete except with certain qualifying words; bill of health, bill of sale etc.)

Bill as a noun:

A draft of a law, presented to a legislature for enactment; a proposed or projected law.

Bill as a noun (obsolete, legal):

A declaration made in writing, stating some wrong the complainant has suffered from the defendant, or a fault committed by some person against a law.

Bill as a noun (US):

A piece of paper money; a banknote.

Bill as a noun:

A written note of goods sold, services rendered, or work done, with the price or charge; an invoice.

Bill as a noun:

A paper, written or printed, and posted up or given away, to advertise something, as a lecture, a play, or the sale of goods

Bill as a noun:

A writing binding the signer or signers to pay a certain sum at a future day or on demand, with or without interest, as may be stated in the document. A bill of exchange. In the United States, it is usually called a note, a note of hand, or a promissory note.

Bill as a noun:

A set of items presented together.

Bill as a verb (transitive):

To advertise by a bill or public notice.

Bill as a verb (transitive):

To charge; to send a bill to.

Bill as a noun:

The bell, or boom, of the bittern.

Greenback as a noun (US):

Any bill that is legal tender in the US (originally printed with green and black ink) issued by the Federal Reserve.

Greenback as a noun:

The United States dollar.

Greenback as a noun:

A unit of American currency issued during the Civil War by the Treasury Department.