Familiar, friendly term for a middle-aged man, often used by children or in casual speech. Can refer to one's own uncle or an unrelated older man.
The middle-aged man next door always gives me candy.
Hey mister, is there a post office around here?
The everyday counter for people: 一人 (ひとり), 二人 (ふたり), 三人 (さんにん).
More formal than 人 — used for headcounts in reservations, staff lists, and announcements (5名様).
A contracted, familiar form of おじちゃん, itself a diminutive of おじさん (uncle). The gemination (っ) adds a casual, affectionate tone.