Genres and Themes of Anime/Manga

While like any other type of media/literature, anime and manga have been placed into general genres. However there are many other themes and categories that anime and manga are placed in. Most of these specific terms are difficult to understand considering their Japanese origin but this list of definitions I hope can help create a better interpretation.
Most of these are thanks to the Anime article from wikipedia.org. I do not lay claim to any of these definitions in quotes, but will only allow myself to expand on these in my own words.

"Major Genres"

"Action/Adventure primarily focuses on battles, war, and physical competition. Martial arts, weapon fighting, or other action oriented material are usually featured. Examples: Naruto or One Piece."

"Drama primarily has a high degree of character development and emotional themes. Many center on relationship complications. Examples: Fushigi Yūgi or Kare Kano. "

"Game Based primarily revolves around some sort of card or board game. Examples: Yu-Gi-Oh! or Hikaru no Go. "

"Horror use darker and/or supernatural themes. Examples: Vampire Hunter D series or Chrono Crusade. "

"Science fiction consists of futuristic elements, particularly featuring future science and technology. They can be drawn from current scientific studies and inventions or created to meet the needs of the world. Examples: Ghost in the Shell or Royal Space Force: The Wings of Honneamise "

"Progressive or "Art films" are extremely stylized. Examples: Sayonara Zetsubō Sensei or 5 Centimeters Per Second. "

"Demographic" Themes
These give a clear understanding of the audience the series is intended for.

"Shōjo is Japanese for "young lady" or "little girl". These are generally targeted at girls. Examples: Fruits Basket or Mermaid Melody Pichi Pichi Pitch."

"Shōnen is Japanese for "young boy". Examples: Dragon Ball Z or Digimon."

"Seinen is Japanese for "young man" and normally includes teenage or young male adults. Examples: Oh My Goddess! or Cowboy Bebop "

"Josei is Japanese for "woman". Examples: Gokusen or Honey and Clover."

"Kodomo is Japanese for "child". All children's series fall into this category. Examples: Hello Kitty or Hamtaro. "

"Thematic" Genres

"Bishōjo is Japanese for "beautiful girl", and a blanket term that features pretty girl characters. Sometimes conflated with Moè. Examples: Magic Knight Rayearth or Negima."

"Bishōnen is Japanese for "beautiful boy", and a blanket term that can be used to describe any anime that features "pretty" and elegant boys and men. Examples: Fushigi Yūgi or The Wallflower."

"Sentai is literally a "fighting team" in Japanese. It refers to any show that involves a superhero team. Examples: Cyborg 009 or Voltron. "

"Robot/Mecha features real robots or super robots. Examples: Mobile Suit Gundam or Mazinger Z respectively." Full Metal Panic is also another example.

"Post-Apocalyptic simply deals with a post-apocalyptic world. Examples: Fist of the North Star or Nausicaä of the Valley of the Wind. "

"Mahō shōjo is a subgenre of shōjo known for "Magical Girl" stories. These stories involves teenage or pre-teen girls who receive magical accessories that allows them to transform into magical warriors. Most magical girl anime involves a girl reciting a phrase before undergoing an intricate transformation sequence which shows the girl being magically dressed or an magical artifact forming it's shape into the girl's hand. These sequences are collectively known in anime as henshin. Examples: Sailor Moon or Cardcaptor Sakura. "

"Mahō shōnen is a male equivalent of Mahō Shōjo. Examples: D.N.Angel or Fullmetal Alchemist "

"Moé features characters with perky, cute, weak, or naïve behaviors. In some way, they are not overly independent.Examples: A Little Snow Fairy Sugar. "

"Expertise specializes with a specific topic in depth. Topics range from sports, the arts, and cooking. Examples: Eyeshield 21 with football, or Yakitate!! Japan with bread-making. "

"Lolicon ("Lolita Complex") is the sexualization of under-aged female characters, the name coming from the titular character of Vladimir Nabokov's Lolita. Example: Kodomo no Jikan"

"Shotacon ("Shōtarō Complex") is the sexualization of under-aged male characters, the name coming from the lead child actor from Tetsujin-nijūhachi-gō. Example: Papa to Kiss in the Dark "

• One thing I've noticed about the loli and shota themes is that it doesn't necessarily mean the person is under-aged, just that they look it. For example: Honey from "Ouran Host Club" or Konata from "Lucky Star" who are both in High School but are called 'Loli' because of their appearance to be much younger.

"Harem is a genre which focuses on a male character surrounded by the romance of multiple female characters. Typically, the male cohabits with at least one female. It is usually marketed as a Shōnen or Seinen. Examples: Ranma ½ or Love Hina. "

"Reverse Harem reverses the gender balance in harem, where a female character is romantically involved with many male characters. It is more often than not a Shōjo or Josei Anime. Examples: Ouran High School Host Club or Fruits Basket."

"Magical girlfriend is more accurately termed Exotic Girlfriend. This genre focuses on the romantic relationship (and cohabitation) between a man and at least one woman of extraordinary origins such as alien (Tenchi Muyo!, Urusei Yatsura), supernatural (Oh My Goddess!), or technological (Chobits). Often considered a subgenre of Harem."

"Ecchi is Japanese for "indecent sexuality", derived from the Japanese pronunciation of the letter "H", (the origin of the term is not well known, even in Japan. See main article for more information.) Sexual humor and fan service are prevalent. Examples: Oruchuban Ebichu or He Is My Master. "

"Hentai is Japanese for "abnormal" or "perverted". This term is synonymous to pornography or erotica, as hentai content specifically consists of such. Examples: La Blue Girl or Bible Black."

"Shōjo-ai or Yuri is Japanese for "girl-love". These focus on love and romance between female characters. It is often being replaced by the term "Girls Love" (GL). Yuri is like Shōjo-ai, but sometimes involves older characters or explicit sexual activity. Examples: Revolutionary Girl Utena or Kannazuki no Miko."

"Shōnen-ai is Japanese for 'boy-love'. These focus on love and romance between male characters. The term "Shōnen-ai" is being phased out in Japan due to its other meaning of pederasty, and is being replaced by the term "Boys Love" (BL). Examples: Loveless or Gravitation"

"Yaoi is like "Shōnen-ai" but often involving older characters and explicit sexual activity. Examples: Sensitive Pornograph or Until the Full Moon"

Hope this was helpful to any new or curious fans.
If you'd like a second opinion on some of these definitions I recommend 'Lexicon' from ANN.