ˈpen.ˌtēn noun
( -s )
Etymology: International Scientific Vocabulary penta- + -ene
: either of the two normal amylenes obtained from gasoline:
a. : the alpha or 1-isomer CH 3 CH 2 CH 2 CH . CH 2 — called also alpha-n-amylene, 1-pentene
b. : the beta or 2-isomer CH 3 CH 2 CH . CHCH 3 — called also beta-n-amylene, 2-pentene