herabsetzen
to reduce
To reduce or lower the price, value, amount, or level of something.
Das Geschäft hat die Preise für Winterjacken stark herabgesetzt.
The store greatly reduced the prices of winter jackets.

to reduce / to belittle
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to reduce
To reduce or lower the price, value, amount, or level of something.
Das Geschäft hat die Preise für Winterjacken stark herabgesetzt.
The store greatly reduced the prices of winter jackets.

'Herabsetzen' (to reduce / to belittle) is a separable verb. The prefix 'herab-' comes at the end in a main clause. In a subordinate clause or with a modal verb, the verb stays together.
Der Händler setzt die Preise für Obst herab.
The merchant reduces the prices of fruit.
The verb consists of the directional syllable 'herab' (downward) and the verb 'setzen' (to set/put). So the basic idea is to 'set' something at a lower level, whether it is a price or a person's reputation.
Man sollte die Dosis des Medikaments langsam herabsetzen.
One should reduce the dose of the medication slowly.
The object of the sentence reveals the meaning. If it is about numbers, prices, or quantities, it means 'reduzieren' (to reduce). If it refers to a person or their performance, it means 'abwerten' (to devalue/belittle).
Die Firma musste die Produktion herabsetzen.
The company had to reduce production.
In the meaning 'reduzieren' (to reduce), the verb is often combined with measurable things. Typical objects are: reduce the price, the costs, the speed, or the requirements.
Wegen der Bauarbeiten wurde die erlaubte Geschwindigkeit auf 30 km/h herabgesetzt.
Because of the construction work, the permitted speed was reduced to 30 km/h.
When 'herabsetzen' (to belittle) refers to people, it has a strongly negative meaning. It describes the attempt to deliberately diminish a person's worth or reputation.
Niemand hat das Recht, dich vor anderen herabzusetzen.
No one has the right to belittle you in front of others.
to increase
'erhöhen' and 'herabsetzen' are opposites when it comes to values, prices, amounts, or a level. 'erhöhen' means that something is made larger or higher. 'herabsetzen' means that something is made lower or reduced. Especially with prices, 'herabsetzen' sounds natural when a store makes something cheaper. With people, 'herabsetzen' can also mean to belittle someone, but for the opposite of 'erhöhen', the meaning 'to reduce' is the important one.

Das Geschäft hat den Preis für die Jacke kurz vor dem Winter herabgesetzt.
The shop reduced the price of the jacket shortly before winter.
Vor dem Termin erhöhen wir die Heizung ein wenig, weil es in der Küche kalt ist.
Before the appointment, we turn up the heating a little because it is cold in the kitchen.