1. 延长的：prolongation 延伸 | prolonged 延长的 | prolusion 序言

2. 持续很久的：prolongation 伸长 | prolonged 持续很久的 | prolongedantifoulingpower 长效防污能力

3. 持久的：Trivial 微不足道的 | Prolonged 持久的 | Commissariat 军粮供应

1. 长期的；持续很久的；时间长的
A prolonged event or situation continues for a long time, or for longer than expected.

e.g. ...a prolonged period of low interest rates.
长期的低利率
e.g. ...a prolonged drought.
长期的干旱

adj

1. drawn out or made longer spatially

e.g. Picasso's elongated Don Quixote
lengthened skirts are fashionable this year
the extended airport runways can accommodate larger planes
a prolonged black line across the page

Synonym: elongatedextendedlengthened

2. relatively long in duration
tediously protracted

e.g. a drawn-out argument
an extended discussion
a lengthy visit from her mother-in-law
a prolonged and bitter struggle
protracted negotiations

Synonym: drawn-outextendedlengthyprotracted