Adjacent, adjoining, contiguous, abutting, tangent, conterminous and juxtaposed all mean being in close proximity.
Adjacent does not always imply actual contact but it does indicate that nothing of the same kind comes between; adjacent lots are in contact, but adjacent houses may or may not be.
- it is not likely that pure accident caused three adjacent windows to take a Spanish tone
—Henry Adams
Objects are adjoining when they meet and touch at some line or point of junction.
- adjoining estates
- adjoining rooms
Contiguous adds to adjoining the implication of meeting and touching on one side or a considerable part of one side.
- streets lined with rows of contiguous houses
It may be used figuratively of events as well as of objects.
- adjacent events need not be contiguous; just as there may be stretches of a string which are not occupied by beads, so the child may experience uneventful periods of time
—Jeans
Abutting is usually applied to something that borders on or is in contact with something else, often with the implication of the termination of one thing by the other.
- land abutting on the road
- the north wall, to which abutting rooms were added
—Hussey)
Tangent implies contact at a single point. Its literal use is chiefly geometrical.
- a line tangent to a curve
But in figurative and especially in absolute use it often stresses the general apartness rather than the single point of contact.
- his critics . . . went off at a tangent
—Carson - horror of the tangent, the extreme, the unconventional
—Norman Douglas - that moment when a whistle’s final blow shall signal the deploy and we disperse alone, and tangent to the universe
—Wolff
Objects are conterminous which border on each other or have a common boundary.
- defending the side of Germany conterminous to France
—Lecky
Conterminous applies also to things having the same bounds, limits, or ends.
- the civil and the ecclesiastical parishes in England are sometimes, but not always, conterminous
Things are juxtaposed when they are placed side by side.
- disputes about water rights were almost inevitable between closely juxtaposed communities with expanding populations
—Childe
Especially so as to permit comparison or contrast.
- Juxtaposed ideas
- opulence wildly juxtaposed to unbelievable poverty
—Vanya Oakes