What is the collective noun for problems?

There isn't a single, universally accepted collective noun for "problems". However, here are some options you could use, depending on the context:

Formal:

* A plethora of problems: This emphasizes the large number of problems.

* A series of problems: This suggests a sequence or progression of problems.

* A multitude of problems: Similar to "plethora", this highlights the vastness of the problems.

Informal:

* A mess of problems: This conveys a sense of disarray and difficulty.

* A pile of problems: This implies a heavy burden of problems.

* A whole bunch of problems: This is a casual way to refer to a lot of problems.

More specific:

* A knot of problems: This is a good choice if the problems are intertwined and complex.

* A web of problems: This is similar to "knot" and implies interconnectedness.

Ultimately, the best collective noun for "problems" will depend on the specific situation and the desired tone.