Auxiliary Verbs

In Japanese, auxiliary verbs are auxiliaries which are verbs. This single English term, "auxiliary verb," has been used to refer to various, completely different things in Japanese, like:

1. hojo-doushi 補助動詞
   "Support verbs."
   Verbs that come after the te-form of another verb, or the adverbial form of an adjective.
   Example: in tabete-iru 食べている, "to be eating," the verb auxiliary verb ~iru ～いる.
2. fukugou-doushi 複合動詞
   "Compound verbs."
   The ones composed of two verbs, where the suffix is the auxiliary verb.
   Example: in tabe-yagatta 食べやがった, "dared to eat [it]," the auxiliary verb ~yagaru ～やがる.
3. jodoushi 助動詞
   "Helper verbs."
   Verbs, and other morphemes, that come after one of the basic forms of another word.
   Example: in tabesaserareru 食べさせられる, "to be forced to eat [it]," the auxiliaries saseru and rareru.
4. Light verbs.
   Like suru する, its irregular potential form, dekiru できる, aru ある, and naru なる.

In Japanese, sometimes the term hojo-doushi is used, perhaps mistakenly, to refer to the suffixes in fukugou-doushi, and even to some jodoushi, which, as far as I'm aware, aren't technically hojo-doushi, they just kind of work like auxiliary verbs.