◇ Ordinal Adverbs
序數副詞
序數副詞就是序數（第一、第二…）當作副詞使用，在寫作時能讓讀者更清楚理解文意。序數副詞其實有兩種寫法，像是「第一」可以寫成 first 和 firstly，到底這兩個有什麼差別呢？在大部分情況，這兩者是可以替換的，例如 "Firstly, the pharaoh was known as the living embodiment of the male god Horus." 和 "First, the pharaoh was known as the living embodiment of the male god Horus." 意思相同。但序數 +ly 的用法其實有爭議，有些人認為此用法不正確，因此正式寫作時建議避開 +ly 的用法。最後需要注意整篇文章使用一致的系統，若第一點用 firstly ，第二點一定要用 secondly，而非 second。
Example：
1. This plan definitely won't work. Firstly, we don't have enough money. Secondly, we are shot-staffed.
這個計畫依定不會成功，首先，我們沒有足夠的資金，再來是我們人手不足。
2. The pandemic is not contained in the slightest. Firstly, the death toll is still rising. Secondly, we don't have a cure yet.
這場疫情還沒有完全被控制。第一，死亡人數仍然在上升。其二，我們沒有解藥。
3. The railway system here is well-developed. First, it reaches the most remote village. Second, it rarely has any accidents and is always on time.
這裡的鐵路系統相當成熟。首先，它深入最偏遠的鄉村，在來是它很少發生事故，也很準時。