inter-, intra-

The meanings of these two prefixes differ significantly. The prefix -inter means “between or among.” Thus, interstate commerce is business conducted across state lines. The prefix -intra, however, means “within or in.” Thus, intrastate commerce is business conducted within a single state.

As with most words beginning with a prefix, no hyphen comes between the prefix and the root word. For a complete discusion, see the Punctuation section of Grammar.com. Click here for the beginning of that discussion.

Example: The supervisor sent an interoffice memo to all the branches and urged them to send an intraoffice memo to their staff members.