詞根plain, plaint= to beat the breast 捶胸 , 引申為「抱怨」
1.complain [kmplen] v. 抱怨
(com 加強+ plain 捶胸，引申為「抱怨」 → 抱怨)
The old man complained about the hot weather.老人抱怨天氣炎熱。
I'm going to complain to the manager about this.
我要就這件事向經理投訴。
How can you complain about higher taxes?
你怎麼能抱怨稅費的提高呢？
I was too cowardly to complain. 我太膽小，不敢抱怨。
2.complaint [kmplent] n. 抱怨，訴苦，投訴
(com 加強+ plaint 抱怨，complain的名詞 → 抱怨)
a letter of complaint投訴信
This is a cause of complaint. 這是抱怨的原因。
The most common complaint is about poor service.
最常見的投訴與服務差有關。
I'd like to make a complaint about the noise.
我要就噪音問題提出投訴。
I believe you have a complaint against one of our nurses.
我認為你對我們的一位護士有怨言。
I've got no complaints about them
對他們我沒什麼意見。
3.plaint[plent] n. 悲嘆，抱怨
civil plaint 民事訴狀
A plaint is a complaint or a sad cry.
To him I will bring my plaint. 我會對他訴說。
4.plaintiff [plentf] n. 原告，起訴人
(plain捶胸，引申為「抱怨」 +tiff 表示名詞→ 原告)
Who appeared for the plaintiff? 誰替原告出庭？
Both the plaintiff and the defendant have the right to appeal to the higher court.原告和被告都有權向上級法院上訴。
Can defendant claim against the plaintiff?
被告能針對原告提出主張嗎？
The onus of proof is on the plaintiff.
舉證責任在原告身上。
5.plaintive [plentv] adj. 痛苦的，傷心的
（plain 捶胸，引申為「抱怨」 + tive …的→ 捶胸頓足 → 傷心的）
a plaintive cry/voice 悽楚的哭泣 / 聲音
Her voice was small and plaintive.
她的聲音微弱而哀傷。
I heard a plaintive cry. 我聽到一聲悲傷的哭泣。
Her voice was a little plaintive. His being looked down upon made him sick.她的聲音有點兒傷感。他被人冷落使他很傷感。
Somewhere in the audience an old woman's voice began plaintive wail.
觀眾席裡，一位老太太傷心地哭起來。
Years is a song, a plaintive, the songs, there is no one at the beginning and end of the song.
歲月是一首歌，一首哀怨、悽婉的歌，一首沒有開頭和結尾的歌。
They lay on the firm sands, listening to the plaintive cry of the seagulls.
他們躺在堅實的沙灘上，聽著海鷗的哀鳴。
6. plaintiveness n. 悲哀,哀傷
（plaintive痛苦的，傷心的+ness 名詞後綴→悲哀,哀傷）
He asks in a tone that verges on plaintiveness, 'I'm trying to conserve my voice.
他是以一種近乎哀傷的語氣要求說，我想保護嗓子。