Terminology confusion- Mycorrhizae, Mycorrhiza, Mycorrhizal Fungi

What is the difference between Mycorrhizae, Mycorrhiza and Mycorrhizal Fungi.  Every time I think I figure out the difference, I read something that confuses my understanding.  Sometimes in the context of what I'm reading, it seems like one is a verb (ie. the relationship between the plant/fungi) as opposed to the thing itself, a noun. Is Mycorrhizae plural and Mycorrhiza singular or is it just pronunciation- I say tomAto, you say tomAHto? I'm beginning to think that each term is used improperly a lot as the understanding of it is relatively "new" in the scientific scheme of things. Can someone clarify for me?

It's quite possible that stuff you are reading has the words used incorrectly, which makes it pretty difficult to get your head around it.

Wikki seems to have it about right -Mycorrhiza

mycorrhiza is singular
mycorrhizae or mycorrhizas is plural
mycorrhizal is an adjective

To use examples from the wikki article

"A mycorrhiza (Greek: μυκός, mykós, "fungus", and ρίζα, riza, "root",[1] pl. mycorrhizae or mycorrhizas) is a symbiotic association composed of a fungus and roots of a vascular plant." Here the word used is a noun, not for the fungus or the plant, but for the association between them

"In a mycorrhizal association, the fungus colonizes the host plant's roots, either intracellularly as in arbuscular mycorrhizal fungi" Here the word is an adjective, describing the association. Anther example from the article is "The roots in the relationship, and the plants themselves are referred to as mycorrhizal if mycorrhizae are formed".

Does that help?

That does help!  Thank you.  So if I see a bag of organic fertilizer that says "contains mycorrhizae," that's not really the correct terminology.  It should say contains mycorrhizal fungi.

Let me see if I can be of help here.

First, Burra showed you the "definitions" and a couple of example sentences for usage.

If you see a bag of organic fertilizer and it says "contains mycorrhizae" what they are referring to is that the spores or spawn are part of the fertilizer.
They are also letting you know there are many of the spores or many threads of spawn (spawn is also referred to as hyphae),
which are what come as a result of the spores sprouting (becoming active) and growing the organisms that will eventually reach the point where the density is high enough for fruiting (which is how they reproduce for the purpose of spreading far away from the parent plant).  

When you use that bag of fertilizer the spores or spawn will begin to grow, thus turning into mycorrhizal fungi.  
The organisms are identified by mycorrhiza (one single cell), mycorrhizae (many cells, of the same species (each cell is one organism ready to reproduce)), or mycorrhizas (many different species).
The action they perform in the soil is mycorrhizal.

Does that help?  I can delve deeper if needed.