die Gelegenheit
opportunity
A favorable time or suitable situation to do something specific; a chance.
Nutze die Gelegenheit, um Fragen zu stellen.
Use the opportunity to ask questions.

opportunity
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opportunity
A favorable time or suitable situation to do something specific; a chance.
Nutze die Gelegenheit, um Fragen zu stellen.
Use the opportunity to ask questions.

'Gelegenheit' is related to the adjective 'gelegen', which means 'suitable' or 'convenient'. So a 'Gelegenheit' (opportunity) is a situation that 'gelegen kommt' (comes at a convenient time), meaning it fits well right now.
Dein Anruf kommt mir gerade sehr gelegen.
Your call is very convenient for me right now.
'Gelegenheit' is often combined with certain verbs that express how someone deals with a chance. Common collocations are 'die Gelegenheit nutzen' (to use the opportunity), 'die Gelegenheit ergreifen' (to seize the opportunity), or 'eine Gelegenheit verpassen' (to miss an opportunity).
Er hat die Gelegenheit ergriffen und sich auf die Stelle beworben.
He seized the opportunity and applied for the position.
'Gelegenheit' is very often used with an infinitive construction to describe what the opportunity is for. The pattern is: 'die Gelegenheit haben/bieten/geben, etwas zu tun' (to have/offer/give the opportunity to do something).
Auf der Konferenz hatte ich die Gelegenheit, mit vielen Experten zu sprechen.
At the conference, I had the opportunity to speak with many experts.
The expression 'bei Gelegenheit' is used to postpone a meeting or action indefinitely into the future. It signals that there is no concrete plan.
Ich rufe dich bei Gelegenheit mal an.
I'll give you a call sometime when I get the chance.
time / mark
'das Mal' and 'die Gelegenheit' can both have to do with a suitable moment. 'das Mal' counts or refers to a single event in a series: 'dieses Mal' (this time), 'nächstes Mal' (next time), 'jedes Mal' (every time). 'die Gelegenheit' means a chance or suitable situation in which you can do something. It does not necessarily say that something has happened several times before. Learners may confuse the words because 'nächstes Mal' and 'bei nächster Gelegenheit' sound similar. 'Nächstes Mal' fits with a repetition, while 'bei Gelegenheit' means more like: when the chance comes up.

Bei Gelegenheit möchte er seinen Freunden die neue Wohnung zeigen.
When he gets the chance, he would like to show his friends the new apartment.
Ich frage meine Tante das nächste Mal nach dem alten Foto.
Next time, I will ask my aunt about the old photo.