also: だいい
captain (Army/USMC/USAF); lieutenant (Navy); flight lieutenant (RAF etc.)
Military rank; the exact equivalent depends on the service branch. The reading だいい was used by the Imperial Japanese Navy.
He was promoted to captain in the Army.
The navy lieutenant gave orders to his subordinates.
He was promoted to captain last year.
少尉 is the lowest commissioned officer rank, whereas 大尉 (captain/lieutenant) is a senior rank two steps above it, and the similar kanji make the two easy to confuse.
Used for people, especially in formal or seat/reservation contexts.
air force captain
Standard kanji form; the reading たいい is the most common.
Reading used historically by the Imperial Japanese Navy; not used in modern contexts.
From 大 (great) + 尉 (military officer rank). The reading だいい is a historical variant used by the Imperial Japanese Navy.