Neighbour chord
In harmony, a neighbour chord is a chord that occurs in a progression that starts with a chord "X" and ends with the same chord "X" (in the same position). It can be used to prolong a harmony.1
You may see the neighbour chord be called a subordinate harmony.
Examples
Example 1
Even though this is commonly thought of as a cadential progression, it can be thought of as a simple prolonged progression of I. Because the melody doesn't emphasize scale degree 1, it doesn't sound as much like a cadence.

Example 2
