多久 means 'how long.' 很久 means 'a long time.' 好久不见 is one of the most common Chinese greetings.
history
好久不见 (long time no see) is believed to be the origin of the English expression 'long time no see,' borrowed from Chinese pidgin English.
Components
pictograph
久jiǔ
long (in time)
Originally a picture of a person being moxibustioned - a stick pressed against the body for a long burn. The cautery sense later split off to 灸; 久 kept the duration meaning through phonetic loan and is no longer cleanly decomposable. Indexed under Kangxi #4 丿 (piě) by stroke shape, not by structure.
Filed under radical 丿 (piě, #4) by convention. 丿 is not a separate component in 久, so no strokes are highlighted.
