The difference between Junk and Scrap

When used as nouns, junk means discarded or waste material, whereas scrap means a (small) piece.

When used as verbs, junk means to throw away, whereas scrap means to discard.

check bellow for the other definitions of Junk and Scrap

Junk as a noun:

Discarded or waste material; rubbish, trash.
Junk as a noun:

A collection of miscellaneous items of little value.
Junk as a noun (slang):

Any narcotic drug, especially heroin.
Junk as a noun (slang):

The clothed genitalia.
Junk as a noun (nautical):

Salt beef.
Junk as a noun:

Pieces of old cable or cordage, used for making gaskets, mats, swabs, etc., and when picked to pieces, forming oakum for filling the seams of ships.
Junk as a noun (dated):

A fragment of any solid substance; a thick piece; a chunk.

Examples:

"rfquotek Lowell"

Junk as a verb (transitive):

To throw away.
Junk as a verb (transitive):

To find something for very little money (meaning derived from the term junk shop)

Examples:

"(On Facebook, a record collector wrote:) "The newest addition to my Annette Hanshaw collection, I junked this beautiful flawless E-copy within walking distance from my house."

Scrap as a noun:

A (small) piece; a fragment; a detached, incomplete portion.

Examples:

"I found a scrap of cloth to patch the hole."
Scrap as a noun (usually, in the plural):

Leftover food.

Examples:

"Give the scraps to the dogs and watch them fight."
Scrap as a noun:

The crisp substance that remains after drying out animal fat.

Examples:

"pork scraps"
Scrap as a noun (uncountable):

Discarded objects (especially metal) that may be dismantled to recover their constituent materials, junk.

Examples:

"That car isn't good for anything but scrap."
Scrap as a noun (ethnic slur, offensive):

A Hispanic criminal, especially a Mexican or one affiliated with the Norte gang.

Scrap as a verb (transitive):

To discard.
Scrap as a verb (transitive, of a project or plan):

To stop working on indefinitely.
Scrap as a verb (intransitive):

To scrapbook; to create scrapbooks.
Scrap as a verb (transitive):

To dispose of at a scrapyard.
Scrap as a verb (transitive):

To make into scrap.

Scrap as a noun:

A fight, tussle, skirmish.

Examples:

"We got in a little scrap over who should pay the bill."