sigma
sigma — 名詞
1. The 18th character in the Greek writing system, written as Σ (uppercase) or σ an
西格馬
希臘字母第18個（Σ, σ, ς）
The 18th character in the Greek writing system, written as Σ (uppercase) or σ and ς (two lowercase forms).
Mauricio learned to write the letter sigma in his Ancient Greek class.
Mauricio 在古希臘文課上學會了怎麼寫西格馬這個字母。
letter name in language-learning context
In maths, the capital sigma (Σ) means you should add up all the terms.
在數學中，大寫的 Σ 代表要把一連串的數字加起來。
capital Σ for summation in mathematics
The lowercase sigma has two forms: σ in the middle and ς at the end of words.
小寫的西格馬有兩種寫法：在單字中間寫 σ，在單字結尾寫 ς。
Reuben wrote the Greek letter sigma on the whiteboard during his presentation.
Reuben 在簡報時把希臘字母西格馬寫在白板上。
Élise typed the word sigma into the search bar to find the Greek symbol.
Élise 在搜尋欄輸入了 sigma 這個詞，想找出那個希臘符號。
文法句型
sigma + [verb]
the letter sigma
用法筆記
Sigma has two lowercase forms depending on position in a word: σ (medial, used everywhere except the end) and ς (final, used only at the end of a word). This distinction matters when writing Greek text. Outside of Greek-language contexts, sigma is most often seen in mathematical notation (Σ for summation) and statistics (σ for standard deviation).