[不可數名詞, 可數名詞]She nodded in affirmation.
她肯定地點了點頭。
appreciation
[不可數名詞] pleasure that you have when you recognize and enjoy the good qualities of sb/sth 欣賞
She shows little appreciation of good music.
她感受不到美好音樂的妙處。
The crowd murmured in appreciation .
人群低聲贊嘆著。
[不可數名詞, 單數] ~ of sth a full or sympathetic understanding of sth, such as a situation or a problem, and of what it involves 理解；體諒；同情
I had no appreciation of the problems they faced.
我沒有體諒到他們所面臨的困難。
[不可數名詞] ~ (of/for sth) the feeling of being grateful for sth 感激；感謝
Please accept this gift in appreciation of all you've done for us.
承蒙鼎力相助，不勝感激，謹備薄禮，敬請笑納。
這兩個詞本意就不同，可能只是再某個語境下讓妳覺得它們意思相同。這種辨析還是弄清楚詞的本意比較好。然後多看例句。