Inf.

Of lower quality

"Anna had always felt inferior to her brother due to poor school grades."

Of lower rank

"an inferior officer"

Located below

Situated below some other organ; said of a calyx when free from the ovary, and therefore below it, or of an ovary with an adherent and therefore inferior calyx.

(grammar) the infinitive mood or mode (a grammatical mood)

(grammar) A non-finite verb form considered neutral with respect to inflection; depending on language variously found used with auxiliary verbs, in subordinate clauses, or acting as a gerund, and often as the dictionary form.

(grammar) A verbal noun formed from the infinitive of a verb.

Not formal or ceremonious.

"an informal get-together"

Not in accord with the usual regulations.

"an informal agreement"

Suited for everyday use.

"informal clothes"

(of language) Reflecting everyday, non-ceremonious usage.