對等連接詞 vs. 副詞

對等連接詞有哪些: For, And, Not, But, Or, Yet, So (FAN BOYS) 都是對等連接詞, Because也是對等連接詞. 顧名思義就是連接兩個對等的架構, 例如連接兩個子句, 兩個名詞. 
對等連接詞的用法:

• 用法1. 子句1 and 子句2 
• 用法2. 子句1, and 子句2

therefore, thus, hence, accordingly, then, 不是對等連接詞, 而是副詞, 不能直接連接兩個相等架構. 副詞的用法:

• 用法1. 子句1, and therefore 子句2
• 用法2. 子句1 and therefore 子句2
• 用法3. 子句1; therefore 子句2
• 用法4. 子句1; 主詞 therefore 動詞
• 用法5. 子句1. Therefore, 子句2

錯誤例句:

• I get up in the morning, then I get dressed. (X) 

因為 then 是副詞, 不能直接連接兩個子句. 正確用法如下 :

• (1) I get up. Then, I get dressed. (O)
• (2) I get up; then I get dressed. (O)
• (3) I get up, and then I get dressed. (O)

Since 可以是副詞也可以是對等連接詞. 
當Since = because的時候, since 就是連接詞. 

• We didn't enjoy the day because the weather was so awful. (O)
• We didn't enjoy the day since the weather was so awful. (O)
• Since the weather was awful, we didn't enjoy the day. (O)