“The two buildings are in close proximity to each other.”
Close Proximity
Proximity means closeness, so 'close' adds no new information.
The comparisoni
“The two buildings are in close proximity to each other. OR The two buildings are close to each other.”
More examplesii
The cities in close proximity to the river developed faster.
The cities near the river developed faster.
Our office is in close proximity to the train station.
Our office is near the train station.
Place sensors in close proximity to the equipment.
Place sensors near the equipment.
The ruleiii
PROXIMITY MEANS CLOSENESS: Proximity by definition refers to the state of being close.
People use 'close proximity' to sound more formal or technical, especially in academic or professional writing. The phrase feels more sophisticated than simply saying 'near' or 'close', so speakers employ it without recognizing the redundancy.
Memory aidiv
The word 'proximity' comes from Latin 'proximus' meaning 'nearest'. If something is 'nearest', can it be anything but 'close'? No—the meaning is already there.