A progression is a gradual development from one state to another.
例句
Both drugs slow the progression of HIV, but neither cures the disease...這兩種藥物都可以延緩艾滋病病情發展，但是都不能治愈這種疾病。I think they saw it as a natural progression for me.我想他們認為這對我來說是順理成章的。
N-COUNT
（事件的）一連串，一系列，連續
A progression of things is a number of things which come one after the other.
例句
...a progression of habitats from dry meadows through marshes to open water.從干燥的草地到沼澤地再到開闊的水面的一系列棲息地
英漢詞典釋義
n.
(事件的)連續;一系列
A progression of disagreements has led to war between those nations.一連串的不和導致那些國家之間爆發了戰爭。
<數>級數
Population is increasing in that country in a geometric progression.那個國家的人口正以幾何級數增長。