die Fülle
abundance
A very large amount or number of something; an excess or plenty.
Er war von der Fülle an Informationen überwältigt.
He was overwhelmed by the abundance of information.

abundance / fullness
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abundance
A very large amount or number of something; an excess or plenty.
Er war von der Fülle an Informationen überwältigt.
He was overwhelmed by the abundance of information.

The noun 'die Fülle' (abundance/fullness) comes from the adjective 'voll' (full). It describes the state when something is full or available in abundance.
Der Korb war voll mit Äpfeln, es war eine Fülle an Obst da.
The basket was full of apples; there was an abundance of fruit.
To say what there is a large amount of, 'Fülle' (abundance) is very often used with the preposition 'an' followed by the dative. For example: 'eine Fülle an Möglichkeiten' (an abundance of possibilities).
Das Museum bietet eine Fülle an interessanten Ausstellungsstücken.
The museum offers an abundance of interesting exhibits.
The idiom 'in Hülle und Fülle' means 'a great deal' or 'in abundance'. It is often used to emphasize that something is available in plentiful amounts.
Auf dem Fest gab es Essen und Trinken in Hülle und Fülle.
At the festival, there was food and drink in abundance.
The meaning 'rundliche Körperform' (rounded body shape) is used only in the context of describing people or their figure. It is often a polite or euphemistic description.
Das Kleid schmeichelte ihrer Fülle.
The dress flattered her fullness.
amount / crowd
'die Menge' and 'die Fülle' can both mean that there is a lot of something. 'die Menge' is neutral and general: it can mean a large, small, or exact quantity. 'die Fülle' tends to emphasize abundance, richness, or variety. It often sounds a little more elevated and fits well with offers, ideas, information, or impressions. The words can be confused because both are possible with large numbers or many things. If you simply want to say how much is there, you usually use 'Menge'. If you want to emphasize the wide selection or rich content, 'Fülle' fits better.

Am Abend sprach sie mit ihrer Kollegin über die Fülle neuer Ideen.
In the evening, she talked with her colleague about the abundance of new ideas.
Vor dem Wochenende ist die Menge der Bestellungen besonders groß.
Before the weekend, the number of orders is especially high.