prefix, suffix
Bound prefix or suffix meaning 'long' in terms of length or duration. Used in compound words; not a standalone adjective.
「長期間」の「長」は「長い」という意味です。
The 長 in 長期間 means 'long'.
「長袖」は「長い袖」のことです。
長袖 means 'long sleeves'.
Standalone adjective meaning 'long'. 長 is its bound combining form used in compounds.
The bound form 長 (なが) is derived from the adjective 長い (ながい), meaning 'long'. It appears in many established compounds.