長～
ちょう～ · chou～ · JLPT N2 · noun
long ~
🐍 長 = long; compounds it as a prefix: 長距離 = long + distance (chou-kyori, long distance)
長 is read chou in compounds like 長編 (long novel) and 長期 (long-term). In each one, 長 means long and attaches to the word after it.
なが～ · naga～ · JLPT N2 · noun
long ~
🐍 長 = long: 長い (nagai) is long, and 長編 (chouhen) is a long-form work
The same root gives 長さ (nagasa), meaning length, and 長生き (nagaiki), meaning long life. Wherever you see 長 at the start of a word, expect the idea of length.