Hall identified four types of culturally elaborated zones: intimate, personal, social, and public. He further subdivided these into “far” and “close” phases:

Intimate distance (0 in.-1 8 in.) At intimate distance, all the senses are activated and the presence of the other person or persons is unmistakable. The close phase (0 in.- 6 in.) is an emotionally charged zone reserved for love-making, comforting,and protecting; the far phase (6in.-18 in.)is the distance where family members and close friends interact. Touch is frequent at both phases of intimate distance.
Personal distance (1.5 f t . 4 ft.) This is the minimum comfortable distance between non-touching individuals. In the close phase (1.5 ft.-2.5 ft.), one can grasp the other by extending the arms. The far phase (2.5 f t . 4 ft.) is defined as anywhere from one arm’s length to the distance required for both individuals to touch hands. Beyond this distance the two must move to make contact (e.g., to shake hands). In essence, this zone constitutes a small protective space.

Social distance (4 ft.-12 ft.) T h s distance is considered non-involving and non-threatening by most individuals. The close phase (4 ft.-7 ft.) is typical of impersonal transactions and casual social gatherings. Formal social discourse and transactions are characteristic of the far phase (7 ft.-12 ft.). T h s is the minimum distance at which one could go about one’s business without seeming rude to others.

Public distance (12 ft. and beyond) At this distance, one can take either evasive or defensive action if physically threatened. Hall noted that people tend to keep at distance from important public figures or from anyone participating at a public function. Discourse at this distance will be highly structured and formalized (lectures, speeches, etc.).

The study of such zones, and of interpersonal behaviors generally, falls under the rubric of proxernics, the term coined by Hall himself. Semiotically, the maintenance of proxemically meaningful zones is explained in terms of spatial codes. The zones themselves are, of course, signs. And the signifieds of these signs are distributed in other codes, such as language, as can be detected as well in the use of space metaphors in common discourse-“Keep your distance,” “They’re very close,” “We’ve drifted far apart,” “You’re trespassing into my personal space,” “I can’t quite get to him,” “Please keep in touch,” and so on.

From Messages, Signs, and Meanings : A Basic Textbook in Semiotics and Communication (2004) by Marcel Danesi