The difference between Turn down and Turn up

When used as verbs, turn down means to refuse, decline, or deny, whereas turn up means to show up.

check bellow for the other definitions of Turn down and Turn up

Turn down as a verb (idiomatic):

To refuse, decline, or deny.

Examples:

"He turned down all our offers of help."
Turn down as a verb (idiomatic):

To reduce the power, etc. of something by means of a control, such as the volume, heat, or light.

Examples:

"Turn down the television so I can hear myself think."

"When it starts to boil, turn down the heat to a simmer."
Turn down as a verb (idiomatic):

To reposition by turning, flipping, etc. in a downward direction.

Examples:

"Turn down the blankets to let them air out."

Turn up as a verb (intransitive):

To show up; to appear suddenly or unexpectedly.

Examples:

"Is this your pencil that turned up in my drawer?"

"I don't like people turning up without an appointment''."
Turn up as a verb (transitive):

To cause to appear; to find by searching, etc.

Examples:

"I spent hours in the archives, but couldn't turn up anything on the alleged criminal."
Turn up as a verb (transitive):

To increase the amount of something by means of a control, such as the volume, heat, or light.

Examples:

"Turn up the radio and sing along."
Turn up as a verb (transitive):

To reposition by rotating, flipping, etc. upwards.

Examples:

"He turned up his collar against the cold."
Turn up as a verb (transitive, nautical):

To belay or make fast a line on a cleat or pin.

Examples:

"Turn up the [[main]] [[halyard]]."
Turn up as a verb (intransitive, slang):

To party hard, especially when involving alcohol or drugs.

Examples:

"We're going to turn up at the [[concert]] tonight."