Anime - Any animation produced in or originating from Japan. Shorthand for Japanese animation.
Bishonen - A good-looking child. Usually reserved for young males like the boy Kouta.
Ecchi - A catch-all for almost any sexual behavior in the genre; Usually reserved for strong but non-explicit, like most of Nyu's antics.
Fan Service - Literally referring to any kind of 'in-joke' or some manner of visual or verbal pun not integral to the plot of a story; in practice, nudity or sexual imagery used to draw in viewers/readers. For example, while Nyu climbing into Kouta's bath is fan service, by that same token, so was her comical effort to get him water while he was sick.
Glomp - A hug that bowls the recipient over; Nyu does this to Kouta more than once.
Harem - Broadly used to describe situations in which a young man lives awkwardly with a group of interested women. Even though at least half of the female cast of Elfen Lied do not have a romantic interest in Kouta, it is still regarded as such.
Manga - Japanese comics, or a piece using this style, usually marked by features such as large eyes, long limbs, speed lines and exclamatory typography. Often marked off by the distinctive personal style of the creator.
Mangaka - Usually, the sole creator, writer and the illustrator of a manga. Collaborations are not unknown, but are rarer. Lynn Okamoto is this for Elfen Lied.
OVA - Original Video Animation, usually something that is not part of a series' broadcast but included in later home video compilations. Rainstorm ~ Regenschauer, which is set inbetween episodes 10 and 11, is an example of this.
Seinen - Manga/anime intended for older teen boys (around 15-16 years of age) and usually young men 18-30 although some for men in their 40s exist; Weekly Young Jump, which introduced Elfen Lied, is an example of a magazine that would carry this.
Tsundere - A person who seems harsh towards a boy on the surface, but hides deeper feelings for him behind this, or the other way around. It is also referred to as "Sugar and Fire personality" (Sugar=dere, Fire=Tsun) Yuka is the best example of this.
Yandere - A person who is initially loving and gentle (or at least innocent) before their devotion becomes destructive in nature, often through violence and/or brutality. It is also referred to as "Sugar and Poison personality" (Sugar=dere, Poison=Yan). Yanderes kill and/or attack others to prevent them from having their loved one taken, or kill and/or attack their loved one to prevent others from having that Yandere's loved one. Yanderes are mentally unstable, and at the worst incredibly deranged and are not mentally sane, often using extreme violence and/or brutality to as an outlet for their emotions. Kaede/Lucy/Nyu is the best example of this in Elfen Lied.
- TVTropes lists that the canonical alignment of the more savage variety and most evil Yanderes are Chaotic Evil . Alingments vary, but if they are a protagonist or side with the protagonist, then they're of the Type I (More chaotic than evil) variety. Chaotic Evil Yanderes may also be a Type II (more evil than chaotic), rarely a Type III (Feral in nature), and, at the worst, a Type IV (As much evil as chaos). The reasons for all of the above are due to similar reasons as Ax Crazy characters. Evil Yanderes that aren't Chaotic Evil are Neutral Evil of the Type II (Immoral and deliberately evil, recognize the difference between right and wrong, at least superficially or that others adhere to it, and willfully and gleefully choose wrong) variety. Yanderes that aren't evil are Chaotic Neutral of the Type IV (Cynical in nature) varieties. It's a rare occurrence for a Yandere to be of an actual good alignment due to their near-Ax Crazy tendencies, and many Yanderes in a good-aligned team tend to be the Token Evil Teammate.