When to use ae vs a for plurals?

1. Is A or AE plural?
2. What words don't change when plural?

Is A or AE plural?

The ‑ae suffix is used for the plural of many non-naturalized, specialist, or unfamiliar nouns ending in ‑a (see ‑a¹) derived from Latin or Greek: antennae is the plural of antenna; larvae of larva; scapulae of scapula, a shoulder-blade; pupae of pupa, a chrysalis.

What words don't change when plural?

The words “moose,” “sheep” and “shrimp” do not have a plural form, but they can be used in singular or plural form as they are. For example: – The moose is/are migrating.