What is the collective nouns tiers?

There isn't a widely accepted collective noun for "tiers". It's not a common enough concept to have developed a specific term.

Here's why:

* Tiers usually refer to levels or ranks in a system (like in a hierarchy or a game).

* Collective nouns are words that describe a group of things.

* While you could use a general collective noun like "group, series, set, system, or structure" to describe tiers, these are less specific and don't capture the hierarchical aspect of "tiers".

If you want to be more specific, you could consider:

* A hierarchy of tiers

* A system of tiers

* A ranking of tiers

Ultimately, the best way to describe tiers depends on the context.