1
- an area of indefinite extent, typically a large one（尤指大片的）面积不定的土地：
large tracts of natural forest.
大片自然森林。
1.1
- poetic/literary an indefinitely large extent of something〈诗/文〉大量, 许多：
the vast tracts of time required to account for the deposition of the strata.
地层沉积所需的大量时间。
2
- a major passage in the body, large bundle of nerve fibres, or other continuous elongated anatomical structure or region（身体的）道, 束：
the digestive tract.
消化道。
词源
late Middle English （in the sense 'duration or course ［of time］'）： from Latin tractus 'drawing, draught', from trahere 'draw, pull'.
- (in the Roman Catholic Church) an anthem of Scriptural verses formerly replacing the alleluia in certain penitential and requiem Masses咏唱（原在罗马天主教某些忏悔或安魂弥撒时用以代替阿利路亚赞美诗所唱的《圣经》韵文圣歌）。
词源
late Middle English: from medieval Latin tractus （cantus） 'drawn-out (song)', past participle of Latin trahere 'draw'.