der Bezug
cover
A removable fabric covering for duvets, pillows, or upholstered furniture.
Ich muss am Wochenende den Bezug der Bettdecke waschen.
I need to wash the duvet cover this weekend.

cover / reference
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cover
A removable fabric covering for duvets, pillows, or upholstered furniture.
Ich muss am Wochenende den Bezug der Bettdecke waschen.
I need to wash the duvet cover this weekend.

'Der Bezug' is the noun related to the verb 'beziehen'. Many meanings become clearer if you think of the verb: 'ein Bett beziehen' (to put a cover on a bed → der Bettbezug, the duvet/bed cover), 'eine Zeitung beziehen' (to subscribe to a newspaper → der Zeitungsbezug, the newspaper subscription), 'sich auf etwas beziehen' (to refer to something → der Bezug auf etwas, the reference to something).
Er bezieht sich in seiner Rede auf eine aktuelle Studie.
In his speech, he refers to a recent study.
You can recognize the meaning of 'Bezug' from the context. If it is about textiles for furniture or beds, it means a cover (m01). If it is about abstract relationships, it means a connection (m02). If it is about newspapers or subscriptions, it means regular receipt (m04).
Ich habe keinen persönlichen Bezug zu diesem Thema.
I have no personal connection to this topic.
The phrase 'Bezug nehmen auf' (to refer to) is a formal fixed expression often used in business letters or emails. It introduces a reference to something previous and requires the accusative.
Ich nehme Bezug auf unser Telefongespräch von letzter Woche.
I refer to our phone conversation from last week.
The expression 'in Bezug auf' (with regard to) functions like a single preposition meaning 'hinsichtlich' or 'bezüglich' (with regard to / concerning). It introduces a topic and takes the accusative. It is typical of formal written language.
In Bezug auf Ihre Bewerbung haben wir noch einige Fragen.
With regard to your application, we still have a few questions.
When 'Bezug' means a fabric cover, it is often used in compound words such as 'Bettbezug' (duvet/bed cover) or 'Kissenbezug' (pillowcase). Typical verbs are 'aufziehen' (to put on), 'wechseln' (to change), or 'waschen' (to wash).
Könntest du mir helfen, den neuen Bezug auf die Decke aufzuziehen?
Could you help me put the new cover on the duvet?
To express a connection, 'Bezug' is often used with the preposition 'zu' (+ dative) or 'zwischen' (+ dative).
Der Film hat einen starken Bezug zur aktuellen politischen Lage.
The film has a strong connection to the current political situation.
connection / association
'Verbindung' and 'Bezug' can both express a connection between things. 'Verbindung' often sounds a bit more general and can also mean real contact or a relationship. 'Bezug' is used especially when showing which topic or matter something belongs to. In texts and conversations, 'in Bezug auf' (with regard to) is very typical when narrowing down a topic. 'In Verbindung mit' (in connection with) fits better when two things work together or are considered together. Learners may confuse the words because both describe a connection. As a guide: 'Bezug' is more like asking 'What does this refer to?', while 'Verbindung' is more like asking 'What is connected to what?'

In Bezug auf die Bewerbung fehlen noch zwei wichtige Dokumente.
With regard to the application, two important documents are still missing.
Die Polizei prüft eine mögliche Verbindung zwischen den beiden Fällen.
The police are investigating a possible connection between the two cases.