adjacent / adjoining
Near versus sharing a boundary.
Both are adjectives. Adjacent means next to or very near; the things may or may not touch. Adjoining means sharing a wall, edge, or border. Two houses across a narrow lane can be adjacent; two row houses with a common wall are adjoining. When the distinction matters, keep it. When it does not, adjacent covers both.
Examples
Use The hotel is adjacent to the station.
Use The bakery expanded into the adjoining shop and doubled its seating.
Avoid The library and the adjoining park are separated by a four-lane road. (Change adjoining to adjacent.)